U.S. patent application number 14/375283 was filed with the patent office on 2015-01-15 for binder for electrodes of lithium secondary batteries, and lithium secondary battery which uses electrode produced using binder for electrodes of lithium secondary batteries.
This patent application is currently assigned to Dai-Ichi Kogyo Seiyaku Co., Ltd.. The applicant listed for this patent is Dai-Ichi Kogyo Seiyaku Co., Ltd.. Invention is credited to Shuichi Ito, Takeshi Miyamura, Katsuo Takahashi.
Application Number | 20150017533 14/375283 |
Document ID | / |
Family ID | 48904896 |
Filed Date | 2015-01-15 |
United States Patent
Application |
20150017533 |
Kind Code |
A1 |
Takahashi; Katsuo ; et
al. |
January 15, 2015 |
BINDER FOR ELECTRODES OF LITHIUM SECONDARY BATTERIES, AND LITHIUM
SECONDARY BATTERY WHICH USES ELECTRODE PRODUCED USING BINDER FOR
ELECTRODES OF LITHIUM SECONDARY BATTERIES
Abstract
To provide a binder that has high adhesiveness to a collector,
does not cause release in press molding, has high flexibility, and
is excellent in binding capability and resistance to an
electrolytic solution, and to provide a lithium secondary battery
that is excellent in charge and discharge characteristics using an
electrode produced with the binder. The binder for an electrode
used contains a hydrophilic group-containing polyurethane as a
water dispersion that contains (A) a polyisocyanate, (B) a compound
that has two or more active hydrogen groups, (C) a compound that
has one or more active hydrogen groups and one or more hydrophilic
groups, and (D) a chain extending agent, or contains an aqueous
resin composition containing a polymer of an unsaturated
polymerizable monomer that is emulsified with the hydrophilic
group-containing polyurethane.
Inventors: |
Takahashi; Katsuo;
(Kyoto-shi, JP) ; Ito; Shuichi; (Kyoto-shi,
JP) ; Miyamura; Takeshi; (Kyoto-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dai-Ichi Kogyo Seiyaku Co., Ltd. |
Kyoto-shi, Kyoto |
|
JP |
|
|
Assignee: |
Dai-Ichi Kogyo Seiyaku Co.,
Ltd.
Kyoto-shi, Kyoto
JP
|
Family ID: |
48904896 |
Appl. No.: |
14/375283 |
Filed: |
January 28, 2013 |
PCT Filed: |
January 28, 2013 |
PCT NO: |
PCT/JP2013/000427 |
371 Date: |
July 29, 2014 |
Current U.S.
Class: |
429/217 ;
524/591 |
Current CPC
Class: |
C08G 18/0823 20130101;
C08G 18/73 20130101; C08G 18/348 20130101; C08G 18/6659 20130101;
C08G 18/4854 20130101; C08F 283/006 20130101; H01M 2220/30
20130101; C08G 18/755 20130101; H01M 10/052 20130101; Y02E 60/10
20130101; C08G 18/3215 20130101; C08G 18/0814 20130101; C08G 18/758
20130101; C08G 18/4213 20130101; C08G 18/44 20130101; H01M 4/622
20130101; H01M 4/621 20130101; Y02T 10/70 20130101; C08G 18/6692
20130101; C08G 18/12 20130101; C08G 18/3228 20130101; C08G 18/12
20130101; C08G 18/3228 20130101; C08G 18/302 20130101 |
Class at
Publication: |
429/217 ;
524/591 |
International
Class: |
H01M 4/62 20060101
H01M004/62; H01M 10/052 20060101 H01M010/052 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 2012 |
JP |
2012-021071 |
Feb 2, 2012 |
JP |
2012-021072 |
Mar 27, 2012 |
JP |
2012-072439 |
Mar 30, 2012 |
JP |
2012-078634 |
Apr 20, 2012 |
JP |
2012-096306 |
Claims
1. A binder for an electrode of a lithium secondary battery,
comprising a hydrophilic group-containing polyurethane that
contains (A) a polyisocyanate, (B) a compound that has two or more
active hydrogen groups, (C) a compound that has one or more active
hydrogen groups and one or more hydrophilic groups, and (D) a chain
extending agent.
2. The binder for an electrode of a lithium secondary battery
according to claim 1, which comprises a water dispersion of the
hydrophilic group-containing polyurethane.
3. The binder for an electrode of a lithium secondary battery
according to claim 2, wherein (B) the compound that has two or more
active hydrogen groups contains one or more kinds of polyols
selected from the group consisting of a polycarbonate polyol, a
polyester polyol having an aromatic ring, and a polyether polyol
having an aromatic ring.
4. The binder for an electrode of a lithium secondary battery
according to claim 3, wherein a content of (B) the compound that
has two or more active hydrogen groups is 30% by mass or more and
75% by mass or less with respect to the polyurethane in the
polyurethane water dispersion.
5. The hinder for an electrode of a lithium secondary battery
according to claim 3, wherein the one or more kinds of polyols
selected from the group consisting of a polycarbonate polyol, a
polyester polyol having an aromatic ring, and a polyether polyol
having an aromatic ring have a number average molecular weight of
300 or more and 3,000 or less.
6. The binder for an electrode of a lithium secondary battery
according to claim 3, wherein the polyurethane water dispersion has
an average particle diameter of 0.005 .mu.m or more and 0.5 .mu.m
or less.
7. The binder for an electrode of a lithium secondary battery
according to claim 3, wherein (C) the compound that has one or more
active hydrogen groups and one or more hydrophilic groups contains
a polyol compound having a carboxyl group.
8. The binder for an electrode of a lithium secondary battery
according to claim 3, wherein the polyurethane water dispersion has
an acid value of 5 mgKOH/g or more and 50 mgKOH/g or less with
respect to the total solid content of the polyurethane.
9. The binder for an electrode of a lithium secondary battery
according to claim 3, wherein (A) the poly isocyanate contains an
alicyclic isocyanate and/or an aromatic isocyanate.
10. The binder for an electrode of a lithium secondary battery
according to claim 2, wherein the hydrophilic group-containing
polyurethane has a crosslinking density of 0.01 or more and 0.50 or
less per 1,000 atomic weight of the polyurethane.
11. The hinder for an electrode of a lithium secondary battery
according to claim 10, wherein (B) the compound that has two or
more active hydrogen groups contains a compound that has three or
more active hydrogen groups.
12. The binder for an electrode of a lithium secondary battery
according to claim 10, wherein (D) the chain extending agent
contains a trifunctional or higher functional polyamine.
13. The binder for an electrode of a lithium secondary battery
according to claim 10, wherein (C) the compound that has one or
more active hydrogen groups and one or more hydrophilic groups
contains a polyol compound containing a carboxyl group.
14. The binder for an electrode of a lithium secondary battery
according to claim 1, which comprises an aqueous resin composition
containing a polymer of an unsaturated polymerizable monomer that
is emulsified with the hydrophilic group-containing
polyurethane.
15. The binder for an electrode of a lithium secondary battery
according to claim 14, wherein the hydrophilic group-containing
polyurethane has a crosslinking density of 0.01 or more and 0.50 or
less per 1,000 atomic weight of the polyurethane.
16. The binder for an electrode of a lithium secondary battery
according to claim 14, wherein (B) the compound that has two or
more active hydrogen groups contains one or more kinds of polyols
selected from the group consisting of a polycarbonate polyol, a
polyester polyol having an aromatic ring, and a polyether polyol
having an aromatic ring.
17. A lithium secondary battery comprising an electrode using the
binder for an electrode of a lithium secondary battery according to
claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to a binder for an electrode
of a lithium secondary battery, and a lithium secondary battery
using an electrode produced with the binder.
BACKGROUND ART
[0002] In recent years, portable electronic equipments, such as a
portable telephone, a notebook computer, a personal digital
assistant (PDA), a camcorder and a digital still camera, are
largely spread, and with increasing demands of miniaturization and
weight saving of the electronic equipments, a battery as a driving
electric power source thereof receives increasing demands of
miniaturization, weight saving, reduction in thickness and increase
in capacity, for which studies are being actively made. A lithium
secondary battery has a high voltage and a good energy density, and
thus has been widely used as an electric power source of a portable
electronic equipment. Associated with the development of the
industry of displays having a small size and a light weight,
however, there is a demand of a battery that has a smaller size and
a lighter weight, and thus a lithium secondary battery is demanded
to have enhanced battery characteristics including a higher driving
voltage, a prolonged service lifetime and a higher energy density
as compared to an ordinary lithium secondary battery. Middle-size
or large-size lithium secondary batteries for automotive use,
industrial use or the like are being developed in recent years, and
there are expectations of developments for enhancing the capacity
and the output power. For satisfying the demands, accordingly,
there are being continuous efforts for enhancing the performances
of the constitutional elements of the lithium battery.
[0003] The characteristics of the battery largely vary depending on
the battery materials used, such as an electrode, an electrolyte
and the like, and in particular, the characteristics of the
electrode may be determined by an electrode active substance, a
collector, and a binder, which imparts an adhesive force
therebetween. For example, the amount and the species of the active
substance used determine the amount of lithium ions capable of
being bonded to the active substance, and thus a battery having a
larger capacity may be obtained by using an active substance in a
larger amount and by using an active substance having a larger
inherent capacity. In the case where the binder has an excellent
adhesive force between the active substances and between the active
substance and the collector, electrons and lithium ions migrate
smoothly within the electrode to reduce the internal resistance of
the electrode, thereby performing charge and discharge with a high
efficiency. A battery having a large capacity requires a composite
electrode for an anode active substance, such as carbon and
graphite, and carbon and silicon, which may suffer large volume
expansion and contraction of the active substance on charge and
discharge, and therefore the binder not only necessarily has an
excellent adhesive force, but also necessarily has excellent
elastic property and maintains the original adhesive force and
restorative force even after undergoing considerable expansion and
contraction of the electrode volume.
[0004] In view of the above points, a fluorine resin, such as
polytetrafluoroethylene and polyvinylidene fluoride, dissolved in
an organic solvent is used as a binder for providing an electrode.
However, a fluorine resin may not have sufficiently high
adhesiveness to a metal constituting a collector and may not have
sufficiently high flexibility, and thus in production of a spiral
wound battery, there are such problems that the resulting electrode
layer suffers cracking, and the resulting electrode layer is
released from the collector. Furthermore, the amount thereof used
is necessarily large for maintaining the sufficient adhesive force,
which may restrict miniaturization, and the use of the organic
solvent mixed therewith disadvantageously makes the production
process complicated.
[0005] A known binder that has high adhesiveness to a metal
constituting the collector and is capable of forming a highly
flexible electrode layer includes a binder formed of
styrene-butadiene rubber (SBR) latex (see PTLs 1, 2 and 3). The
binder is excellent in elastic characteristics but has a small
adhesive force, and on repeated charge and discharge, the electrode
fails to maintain the structure thereof, which may provide an
insufficient service lifetime of the battery. In view of the demand
of enhancement of the battery capacity in recent years, as for the
materials constituting the electrode layer, the content of the
binder component is decreased, and the electrode layer is
press-molded in the production process of the electrode. In the
electrode layer that has a small content of the binder component,
however, the electrode layer is liable to be released from the
collector in the press molding. The phenomenon not only causes
contamination of the press molding machine with the electrode
substance, but also provides such a problem that the reliability of
the battery performance may be deteriorated when the electrode
having an electrode layer that is partially released off is
installed in the battery. The problem may be conspicuous when a
polymer having a low glass transition temperature and high
tackiness is used as the binder component, and thus the problem may
be suppressed by using a latex formed of a polymer that has a high
glass transition temperature, for example, higher than room
temperature. However, the use of a binder formed of a polymer
having a high glass transition temperature provides an electrode
layer that has low flexibility and thus is liable to suffer
cracking, which provides such a problem that the capacity retention
of the battery is deteriorated to fail to provide sufficient charge
and discharge cycle characteristics.
CITATION LIST
Patent Literatures
[0006] PTL 1: JP-A-5-21068 [0007] PTL 2: JP-A-11-7948 [0008] PTL 3:
JP-A-2001-210318
SUMMARY OF INVENTION
Technical Problem
[0009] The invention has been made under the circumstances, and an
object thereof is to provide a binder that has high adhesiveness to
a collector, does not cause release in press molding, has high
flexibility, and is excellent in binding capability and resistance
to an electrolytic solution, and a lithium secondary battery that
is excellent in charge and discharge characteristics using an
electrode produced with the binder.
Solution to Problem
[0010] For achieving the object, the binder for an electrode of a
lithium secondary battery of the invention contains a hydrophilic
group-containing polyurethane that contains (A) a polyisocyanate,
(B) a compound that has two or more active hydrogen groups, (C) a
compound that has one or more active hydrogen groups and one or
more hydrophilic groups, and (D) a chain extending agent.
[0011] In the binder for an electrode of the invention, the
hydrophilic group-containing polyurethane is contained, for
example, in the form of a water dispersion. In this case, (B) the
compound that has two or more active hydrogen groups preferably
contains one or more kinds selected from the group consisting of a
polycarbonate polyol, a polyester polyol having an aromatic ring,
and a polyether polyol having an aromatic ring. The hydrophilic
group-containing polyurethane preferably has a crosslinking density
of 0.01 or more and 0.50 or less per 1,000 atomic weight of the
polyurethane.
[0012] The binder for an electrode of the invention may contain an
aqueous resin composition containing a polymer of an unsaturated
polymerizable monomer that is emulsified with the hydrophilic
group-containing polyurethane.
[0013] The lithium secondary battery of the invention is
constituted by using an electrode using the binder for an electrode
of a lithium secondary battery of the invention.
Advantageous Effects of Invention
[0014] The binder for an electrode of a lithium secondary battery
of the invention has high adhesiveness to a collector, does not
cause release in press molding, has high flexibility, and is
excellent in binding capability and resistance to an electrolytic
solution. A lithium secondary battery that is excellent in charge
and discharge characteristics may be obtained by using an electrode
produced with the binder.
DESCRIPTION OF EMBODIMENTS
[0015] As described above, the binder for an electrode of a lithium
secondary battery of the invention contains a hydrophilic
group-containing polyurethane that contains (A) a polyisocyanate,
(B) a compound that has two or more active hydrogen groups, (C) a
compound that has one or more active hydrogen groups and one or
more hydrophilic groups, and (D) a chain extending agent.
Hereinafter, embodiments of the present invention will be described
in detail.
[0016] The binder for an electrode of a lithium secondary battery
of the invention, in one embodiment, contains a water dispersant of
the hydrophilic group-containing polyurethane, and the component B
contains a polycarbonate polyol, a polyester polyol having an
aromatic ring, and/or a polyether polyol having an aromatic
ring.
[0017] The polyisocyanate as the component A used in the invention
is not particularly limited, and polyisocyanates that are
ordinarily used in this field of art may be used. Specific examples
thereof include an aliphatic polyisocyanate, an alicyclic
polyisocyanate, an aromatic polyisocyanate and an aromatic
aliphatic polyisocyanate. Examples of the aliphatic polyisocyanate
include tetramethylene diisocyanate, dodecamethylene diisocyanate,
hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene
diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine
diisocyanate, 2-methylpentane 1,5-diisocyanate and 3-methylpentane
1,5-diisocyanate. Examples of the alicyclic polyisocyanate include
isophorone diisocyanate, hydrogenated xylylene diisocyanate,
4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane
diisocyanate, methylcyclohexylene diisocyanate and
1,3-bis(isocyanatemethyl)cyclohexane. Examples of the aromatic
polyisocyanate include tolylene diisocyanate, 2,2'-diphenylmethane
diisocyanate, 2,4'-diphenylmethane diisocyanate,
4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl
diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate,
1,3-phenylene diisocyanate and 1,4-phenylene diisocyanate. Examples
of the aromatic aliphatic polyisocyanate include a
dialkyldiphenylmethane diisocyanate, a tetraalkyldiphenylmethane
diisocyanate and
.alpha.,.alpha.,.alpha.,.alpha.-tetramethylxylylene diisocyanate. A
modified product, such as a dimer, a trimer and a burette-modified
isocyanate, of these organic polyisocyanates may also be used.
These compounds may be used solely or as a combination of two or
more kinds thereof. Among these polyisocyanates, an alicyclic
isocyanate and/or an aromatic isocyanate are preferred from the
standpoint of the binding capability and the resistance to an
electrolytic solution, and specifically 4,4'-dicyclohexylmethane
diisocyanate, isophorone diisocyanate and
1,3-bis(isocyanatemethyl)cyclohexane are preferred. The content of
the component A is preferably in a range of from 1/0.85 to 1/1.1 in
terms of equivalent ratio of the isocyanate groups to the total
amount of active hydrogen groups of the component B and the
component C.
[0018] Preferred examples of the compound that has two or more
active hydrogen groups as the component B used in the invention
include a polycarbonate polyol, a polyester polyol having an
aromatic ring, and/or a polyether polyol having an aromatic
ring.
[0019] The polycarbonate polyol used may be a polycarbonate polyol
that is ordinarily used in this field of art without particular
limitation. Specific examples thereof include carbonate polyol of
1,6-hexanediol, carbonate polyol of 1,4-butanediol and
1,6-hexanediol, carbonate polyol of 1,5-pentanediol and
1,6-hexanediol, and carbonate polyol of 3-methyl-1,5-pentanediol
and 1,6-hexanediol. Examples of the commercially available product
thereof include PCDL T-6001, T-6002, T-5651, T-5652, T-5650J,
T-4671 and T-4672, produced by Asahi Kasei Chemicals Corporation,
Kuraray Polyol C-590, C-1050, C-1050R, C-1090, C-2050, C-2050R,
C-2070, C-2070R, C-2090, C-2090R, C-3090, C-3090R, C-4090, C-4090R,
C-5090, C-5090R, C-1065N, C-2065N, C-1015N and C-2015N, produced by
Kuraray Co., Ltd., and ETERNACOLL UH-50, UH-100, UH-200, UH-300,
UM-90(3/1), UM-90(1/1), UM-90(1/3) and UC-100, produced by Ube
Industries, Ltd.
[0020] The polyester polyol having an aromatic ring may be
generally obtained through condensation reaction of a dibasic acid
and a dihydric alcohol. The dibasic acid is not particularly
limited, and specific examples thereof include an aromatic dibasic
acid, such as phthalic acid, isophthalic acid, terephthalic acid,
1,4-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic
acid. The dihydric alcohol is not particularly limited, and
specific examples thereof include an aliphatic glycol, such as
ethylene glycol, diethylene glycol, triethylene glycol, propylene
glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and
3-methyl-1,5-pentanediol, an alicyclic glycol, such as
cyclohexanediol, and an aromatic glycol, such as an alkylene oxide
adduct of bisphenol A.
[0021] Examples of the polyether polyol having an aromatic ring
include an alkylene oxide adduct (such as an ethylene oxide adduct
and a propylene oxide adduct) of bisphenol A.
[0022] As the component B, a polyester polyol and a polyether
polyol may be used in combination with the aforementioned compounds
in such a range that does not impair the effect obtained by the
invention. Specific examples of the polyester polyol include a
polyhydric alcohol, such as ethylene glycol, propylene glycol,
propanediol, butanediol, pentanediol, 3-methyl-1,5-pentanediol,
hexanediol, neopentyl glycol, diethylene glycol, triethylene
glycol, tetraethylene glycol, polyethylene glycol, dipropylene
glycol, tripropylene glycol, 1,4-cyclohexanedimethanol, bisphenol
A, bisphenol F, bisphenol S, hydrogenated bisphenol A,
dibromobisphenol A, dihydroxyethyl terephthalate, hydroquinone
dihydroxyethyl ether, trimethylolpropane, glycerin and
pentaerythritol, and an ester compound of an oxyalkylene derivative
thereof and a polybasic carboxylic acid, a polybasic carboxylic
acid anhydride or a polybasic carboxylate ester. Specific examples
of the polyether polyol include a compound derived from, as a
starting substance, a triol compound, such as glycerin,
hexanetriol, trimethylolethane and trimethylolpropane, and an
alkanolamine, such as triethanolamine, triisopropanolamine and
tributanolamine. Examples thereof also include a compound derived
from, as a starting substance, pentaerythritol as a tetrahydric
alcohol component. The polyether polyol may be synthesized through
polyaddition of an alkylene oxide with the polyhydric alcohol as a
starting substance in the presence of a basic catalyst. Examples of
the alkylene oxide include ethylene oxide, propylene oxide,
butylene oxide and tetrahydrofuran.
[0023] The polycarbonate polyol, the polyester polyol having an
aromatic ring, and/or the polyether polyol having an aromatic ring
preferably have a number average molecular weight of 300 or more
and 3,000 or less. When the number average molecular weight is less
than 300, the binding capability may be lowered, and when the
number average molecular weight exceeds 3,000, the resistance to an
electrolytic solution tends to be lowered.
[0024] To the component B, a single chain low molecular weight
diol, such as ethylene glycol, 1,4-butanediol and
1,4-cyclohexanedimethanol, may be added for localizing urethane
bonds in the molecule.
[0025] As the component B, a polyhydric alcohol and/or an
oxyalkylene derivative of a polyhydric alcohol may be used for
introducing a branched structure in the molecule. Specific examples
thereof include a polyhydric alcohol, such as trimethylolpropane,
glycerin and pentaerythritol, oxyalkylene derivatives thereof, and
an ester compound of the polyhydric alcohol or the oxyalkylene
derivative thereof and a polybasic carboxylic acid, a polybasic
carboxylic acid anhydride or a polyhydric carboxylate ester. It is
preferred that a branched structure is introduced to the
polyurethane to localize urethane bonds, thereby providing such an
effect that an electrode using a binder containing the polyurethane
water dispersion has an enhanced resistance to an electrolytic
solution.
[0026] The content of the component B is preferably 30% by mass or
more and 75% by mass or less with respect to the polyurethane in
the polyurethane water dispersion. When the content is less than
30% by mass, the binding capability may be lowered, and when the
content exceeds 75% by mass, the resistance to an electrolytic
solution tends to be lowered.
[0027] The component C used in the invention is a compound that has
one or more active hydrogen groups and one or more hydrophilic
groups. Examples of the hydrophilic group include an anionic
hydrophilic group, a cationic hydrophilic group and a nonionic
hydrophilic group, specific examples of the anionic hydrophilic
group include a carboxyl group and a salt thereof, and a sulfonic
acid group and a salt thereof, specific examples of the cationic
hydrophilic group include a tertiary ammonium salt and a quaternary
ammonium salt, and specific examples of the nonionic hydrophilic
group include a group containing a repeating unit of ethylene
oxide, and a group containing a repeating unit of ethylene oxide
and a repeating unit of another alkylene oxide.
[0028] Examples of the compound that has one or more active
hydrogen groups and one or more carboxyl groups include a
carboxylic acid-containing compound, such as
2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid,
2,2-dimethylolvaleric acid, dioxymaleic acid, 2,6-dioxybenzoic acid
and 3,4-diaminobenzoic acid, a derivative thereof, and a salt
thereof, and also include a polyester polyol obtained therewith.
Examples thereof also include an amino acid compound, such as
alanine, aminobutyric acid, aminocaproic acid, glycine, glutamic
acid, aspartic acid and histidine, and a carboxylic acid compound,
such as succinic acid, adipic acid, maleic anhydride, phthalic acid
and trimellitic anhydride.
[0029] Examples of the compound that has one or more active
hydrogen groups and one or more sulfonic acid groups (or salts
thereof) include a sulfonic acid-containing compound and a
derivative thereof, such as 2-oxyethanesulfonic acid,
phenolsulfonic acid, sulfobenzoic acid, sulfosuccinic acid,
5-sulfoisophthalic acid, sulfanilic acid,
1,3-phenylenediamine-4,6-disulfonic acid and
2,4-diaminotoluene-5-sulfonic acid, and a polyester polyol, a
polyamide polyol and a polyamide polyester polyol, which are
obtained through copolymerization of these compounds.
[0030] The carboxyl group or the sulfonic acid group is then
neutralized to form a salt, thereby making the polyurethane finally
obtained water-dispersible. Examples of the neutralizing agent in
this case include a nonvolatile base, such as sodium hydroxide and
potassium hydroxide, a tertiary amine compound, such as
trimethylamine, triethylamine, dimethylethanolamine,
methyldiethanolamine and triethanolamine, and a volatile base, such
as ammonia. The neutralization may be performed either before the
urethanization reaction, during the reaction or after the
reaction.
[0031] Examples of the compound that has one or more active
hydrogen groups and one or more tertiary ammonium salts include an
alkanolamine, such as methylaminoethanol and methyldiethanolamine.
The compound may be neutralized with an organic carboxylic acid,
such as formic acid and acetic acid, or an inorganic acid, such as
hydrochloric acid and sulfuric acid, to form a salt, thereby making
the polyurethane water-dispersible. The neutralization may be
performed either before the urethanization reaction, during the
reaction or after the reaction. Among these, a compound obtained
through neutralization of methyldiethanolamine with an organic
carboxylic acid is preferred from the standpoint of the easiness of
emulsification.
[0032] The compound that has one or more active hydrogen groups and
one or more quaternary ammonium salts include a compound obtained
through quaternarization of the aforementioned alkanolamine, such
as methylaminoethanol and methyldiethanolamine, with a halogenated
alkyl, such as methyl chloride and methyl bromide, or a
dialkylsulfuric acid, such as dimethylsulfuric acid. Among these, a
compound obtained through quaternarization of methyldiethanolamine
with dimethylsulfuric acid is preferred from the standpoint of the
easiness of emulsification.
[0033] The compound that has one or more active hydrogen groups and
one or more nonionic hydrophilic groups is not particularly
limited, and a compound that contains 30% by mass or more of a
repeating unit of ethylene oxide and has a number average molecular
weight of from 300 to 20,000 is preferred, examples of which
include a nonionic group-containing compound, such as
polyoxyethylene glycol, polyoxyethylene-polyoxypropylene copolymer
glycol, polyoxyethylene-polyoxybutylene copolymer glycol,
polyoxyethylene-polyoxyalkylene copolymer glycol and monoalkyl
ethers thereof, and a polyester polyether polyol obtained through
copolymerization thereof.
[0034] The compounds as the component C may be used solely or as a
combination thereof.
[0035] The content of the component C is preferably from 5 to 50
mgKOH/g, and more preferably from 5 to 45 mgKOH/g, for the anionic
hydrophilic group-containing compound in terms of acid value
showing the content of the anionic hydrophilic group. When the acid
value is less than 5 mgKOH/g, there may be a problem that the
polyurethane is difficult to be dispersed in water. When the acid
value exceeds 50 mgKOH/g, there may be a problem that the
resistance to an electrolytic solution is lowered. The acid value
may be obtained in terms of the amount of KOH (mg) that is required
for neutralizing the free carboxyl group contained in 1 g in terms
of solid content of the polyurethane water dispersion according to
JIS K0070-1992. In the case where the nonionic group-containing
compound is used, the amount thereof used is preferably from 1 to
30% by mass, and particularly preferably from 5 to 20% by mass, in
the polyurethane in the polyurethane water dispersion. Among these,
the component C is preferably a compound that has one or more
active hydrogen groups and one or more carboxyl groups in a
molecule from the standpoint of the adhesiveness to a
collector.
[0036] The component D used may be a chain extending agent that is
ordinarily used in this field of art and is not particularly
limited, and specific examples thereof used include a diamine and a
polyamine. Examples of the diamine include ethylenediamine,
trimethylenediamine, piperazine and isophoronediamine. Examples of
the polyamine include diethylenetriamine, dipropylenetriamine and
triethylenetetramine. The component D preferably contains a
trifunctional or higher functional polyamine for introducing an
internal crosslinked structure to the polyurethane, thereby
enhancing the resistance to an electrolytic solution. Specific
examples of the polyamine include the polyamines described above.
The content of the component D is preferably such an amount that
provides an equivalent ratio to the isocyanate group of the
component A in a range of from 1/0.5 to 1/0.9 in terms of
isocyanate group/(D) chain extending agent.
[0037] The number average molecular weight of the polyurethane of
the polyurethane water dispersion in the invention is preferably as
large as possible by introducing a branched structure and an
internal crosslinked structure, and is preferably 50,000 or more.
This is because insolubility thereof in a solvent with a large
molecular weight may provide a coated film that is excellent in
resistance to an electrolytic solution.
[0038] The production method of the polyurethane water dispersion
in the invention is not particularly limited. In general, (B) the
compound that has two or more active hydrogen groups, (C) the
compound that has one or more active hydrogen groups and one or
more hydrophilic groups, and (D) the chain extending agent are
reacted with the polyisocyanate as the component A in an amount
that is stoichiometrically excessive to the total amount of the
active hydrogen group having reactivity with the isocyanate group
contained in the components B, C and D (where the equivalent ratio
of the isocyanate group and the active hydrogen group is preferably
from 1/0.85 to 1/1.1) without a solvent or in an organic solvent
having no active hydrogen group to synthesize a urethane prepolymer
having an isocyanate terminal, and after neutralizing or
quaternarizing the anionic hydrophilic group or the cationic
hydrophilic group of the component C depending on necessity, the
prepolymer is emulsified in water. Thereafter, the chain extending
agent as the component D in an equivalent amount that is smaller
than the residual isocyanate group (where the equivalent ratio of
the isocyanate group and the chain extending agent is preferably
from 1/0.5 to 1/0.9) is added thereto, and the isocyanate group in
the emulsion micelle and the chain extending agent as the component
D are subjected to interfacial polymerization to form a urea bond.
According to the procedure, the crosslinking density in the
emulsion micelle is increased, and a three-dimensional crosslinked
structure is formed. The formation of the three-dimensional
crosslinked structure provides a coated film exhibiting excellent
resistance to an electrolytic solution. Thereafter, the solvent,
which is used depending on necessity, is removed, and thereby the
polyurethane water dispersion can be provided. The chain extension
may be performed with water molecules present in the system on
dispersing and emulsifying in water, without the use of the
polyamine or the like as the component D.
[0039] In the synthesis of the urethane prepolymer described above,
such a solvent may be used that is inactive to an isocyanate group
and is capable of dissolving the urethane prepolymer thus formed.
Examples of the solvent include dioxane, methyl ethyl ketone,
dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidine, toluene
and propylene glycol monomethyl ether acetate. These hydrophilic
organic solvents used in the reaction are preferably removed
finally.
[0040] The average particle diameter of the polyurethane water
dispersion used in the invention is preferably in a range of from
0.005 to 0.5 .mu.m from the standpoint of the addition amount, the
coating property and the binding capability.
[0041] The polyurethane of the polyurethane water dispersion used
in the invention preferably has a crosslinking density of from 0.01
to 0.50 per 1,000 atomic weight of the polyurethane. The
crosslinking density referred herein is a value obtained by
calculating based on the expression 1 shown below. Specifically,
the crosslinking density per 1,000 molecular weight of the resin
solid content contained in the polyurethane water dispersion, which
is obtained through reaction of W.sub.A1 g of (A) the
polyisocyanate having a molecular weight MW.sub.A1 and a functional
group number of F.sub.A1, W.sub.A2 g of (A) the polyisocyanate
having a molecular weight MW.sub.A2 and a functional group number
of F.sub.A2, W.sub.Aj g of (A) the polyisocyanate having a
molecular weight MW.sub.Aj and a functional group number of
F.sub.Aj (wherein j represents an integer of 1 or more), W.sub.B1 g
of (B) the active hydrogen-containing compound having a molecular
weight MW.sub.B1 and a functional group number of F.sub.B1,
W.sub.B2 g of (B) the active hydrogen-containing compound having a
molecular weight MW.sub.B2 and a functional group number of
F.sub.B2, W.sub.Bk g of (B) the active hydrogen-containing compound
having a molecular weight MW.sub.Bk and a functional group number
of F.sub.Bk (wherein k represents an integer of 1 or more),
W.sub.C1 g of (C) the compound having one or more active hydrogen
groups and one or more hydrophilic groups having a molecular weight
MW.sub.C1 and a functional group number of F.sub.C1, W.sub.Cm g of
(C) the compound having one or more active hydrogen groups and one
or more hydrophilic groups having a molecular weight MW.sub.Cm and
a functional group number of F.sub.Cm (wherein m represents an
integer of 1 or more), W.sub.D1 g of (D) the chain extending agent
having a molecular weight MW.sub.D1 and a functional group number
of F.sub.D1, and W.sub.Dn g of (D) the chain extending agent having
a molecular weight MW.sub.Dn and a functional group number of
F.sub.Dn (wherein n represents an integer of 1 or more), may be
obtained according to the following expression.
crosslinking density = ( { W A 1 ( F A 1 - 2 ) / MW A 1 } + { W A 2
( F A 2 - 2 ) / MW A 2 } + + { W A j ( F A j - 2 ) / MW A j } ( W A
1 + W A 2 + + W Aj ) + ( W B 1 + W B 2 + + W Bk ) + ( W C 1 + + W
Cm ) + ( W D 1 + + W Dn ) + { W B 1 ( F B 1 - 2 ) / MW B 1 } + { W
B 2 ( F B 2 - 2 ) / MW B 2 } + + { W B k ( F B k - 2 ) / MW B k } (
W A 1 + W A 2 + + W Aj ) + ( W B 1 + W B 2 + + W Bk ) + ( W C 1 + +
W Cm ) + ( W D 1 + + W Dn ) + { W C 1 ( F C 1 - 2 ) / MW C 1 } + +
{ W C m ( F C m - 2 ) / MW C m } ( W A 1 + W A 2 + + W Aj ) + ( W B
1 + W B 2 + + W Bk ) + ( W C 1 + + W Cm ) + ( W D 1 + + W Dn ) + {
W D 1 ( F D 1 - 2 ) / MW D 1 } + + { W D n ( F D n - 2 ) / MW D n }
( W A 1 + W A 2 + + W Aj ) + ( W B 1 + W B 2 + + W Bk ) + ( W C 1 +
+ W Cm ) + ( W D 1 + + W Dn ) ) .times. 1000 [ Expression 1 ]
##EQU00001##
[0042] When the crosslinking density is less than 0.01, there may
be a tendency that the resistance to an electrolytic solution and
the heat resistance are deteriorated, and when it exceeds 0.50,
there may be a tendency that the urethane resin is reduced in
flexibility and is also reduced in binding capability.
[0043] The polyurethane water dispersion of the invention
preferably has a urethane bond amount in the polyurethane of from
150 to 2,000 g/eq, and more preferably from 200 to 1,000 g/eq. When
the urethane bond amount is less than 150 g/eq, the polyurethane
may be reduced in flexibility and thus may be reduced in binding
capability due to the too large urethane bond amount, and when it
exceeds 2,000 g/eq, there may be a tendency that the resistance to
an electrolytic solution and the heat resistance are
deteriorated.
[0044] In the polyurethane water dispersion of the invention, the
urea bond amount in the polyurethane is preferably from 300 to
20,000 g/eq, and more preferably from 400 to 10,000 g/eq. When the
urea bond amount is less than 300 g/eq, the polyurethane may be
reduced in flexibility and thus may be reduced in binding
capability due to the too large urea bond amount, and when it
exceeds 20,000 g/eq, there may be a possibility of causing
deterioration in workability in synthesis, and there may be a
tendency that the resistance to an electrolytic solution and the
heat resistance are deteriorated.
[0045] In the polyurethane water dispersion of the invention, the
total content of the aromatic ring and the alicyclic ring in the
polyurethane is preferably from 10 to 60% by mass, and more
preferably from 20 to 60% by mass. When the total content of the
aromatic ring and the alicyclic ring in the polyurethane is less
than 10% by mass, the resistance to an electrolytic solution may be
deteriorated, and when it exceeds 60% by mass, there may be a
tendency that the polyurethane is reduced in flexibility.
[0046] In the invention, a crosslinking agent may also be used in
the polyurethane water dispersion. Specific examples of the
crosslinking agent include aziridine, oxazoline, modified
polyisocyanate and polyepoxide compounds, and the crosslinking
agents may be used solely or as a combination thereof.
[0047] In another (second) embodiment of the invention, the binder
for an electrode contains the hydrophilic group-containing
polyurethane that has a crosslinking density of 0.01 or more and
0.50 or less per 1,000 atomic weight of the polyurethane.
[0048] In this case, the component A, the component C and the
component D used may be the same as described for the first
embodiment, and the preferred ranges of the contents are also the
same.
[0049] As the compound that has two or more active hydrogen groups
as the component B, for example, a wide range of compounds that
have two or more hydroxyl groups, amino groups or mercapto groups
at a molecular terminal or in a molecule may be used, and known
polyether, polyester, polyether ester, polycarbonate,
polythioether, polyacetal, polyolefin, polysiloxane, fluorine and
vegetable oil compounds may be used. Specific examples thereof
include a polyhydric alcohol, such as ethylene glycol, propylene
glycol, propanediol, butanediol, pentanediol,
3-methyl-1,5-pentanediol, hexanediol, neopentyl glycol, diethylene
glycol, triethylene glycol, tetraethylene glycol, polyethylene
glycol, dipropylene glycol, tripropylene glycol,
1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, bisphenol S,
hydrogenated bisphenol A, dibromobisphenol A, dihydroxyethyl
terephthalate, hydroquinone dihydroxyethyl ether,
trimethylolpropane, glycerin and pentaerythritol, oxyalkylene
derivatives thereof, and an ester compound of the polyhydric
alcohol or an oxyalkylene derivative thereof and a polybasic
carboxylic acid, a polybasic carboxylic acid anhydride or a
polybasic carboxylate ester, and a polyol compound, such as a
polycarbonate polyol, a polycaprolactone polyol, a polyester
polyol, a polthioether polyol, a polyacetal polyol, a
polytetramethylene glycol, a polybutadiene polyol, a castor oil
polyol, a soybean oil polyol, a fluorine polyol and a silicone
polyol, and modified products thereof. Examples of the alkylene
oxide include ethylene oxide, propylene oxide and butylene oxide.
The compound that has two or more active hydrogen groups may be
used solely or as a combination of two or more kinds thereof.
[0050] Among these, a compound having two or more hydroxyl groups
at molecular terminals is preferred, and examples thereof include
ethylene glycol, propylene glycol, propanediol, butanediol,
pentanediol, 3-methyl-1,5-pentanediol, hexanediol, neopentyl
glycol, diethylene glycol, triethylene glycol, tetraethylene
glycol, polyethylene glycol, dipropylene glycol, tripropylene
glycol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F,
bisphenol S, hydrogenated bisphenol A, dibromobisphenol A,
1,4-cyclohexanedimethanol, dihydroxyethyl terephthalate,
hydroquinone dihydroxyethyl ether, and oxyalkylene derivatives
thereof, a polycarbonate polyol, a polycaprolactone polyol, a
polyester polyol, a polthioether polyol, a polyacetal polyol, a
polytetramethylene glycol and a polybutadiene polyol. Examples of
the alkylene oxide for the oxyalkylene derivative include ethylene
oxide, propylene oxide and butylene oxide.
[0051] The component B preferably contains a compound that has
three or more active hydrogen groups having reactivity with the
isocyanate group, for introducing a branched structure to the
polyurethane. Specific examples thereof include a polyhydric
alcohol, such as trimethylolpropane, glycerin and pentaerythritol,
oxyalkylene derivatives thereof, and an ester compound of the
polyhydric alcohol or the oxyalkylene derivative thereof and a
polybasic carboxylic acid, a polybasic carboxylic acid anhydride or
a polyhydric carboxylate ester. The component B may contain a
single chain low molecular weight diol, such as ethylene glycol,
1,4-butanediol and 1,4-cyclohexanedimethanol, for localizing
urethane bonds in the polyurethane. It is preferred as described
above that a branched structure is introduced to the polyurethane
to localize urethane bonds, thereby providing such an effect that
an electrode using a binder containing the urethane water
dispersion has an enhanced resistance to an electrolytic
solution.
[0052] The number average molecular weight of the component B is
not particularly limited and is preferably 50 or more and 5,000 or
less.
[0053] The content of the component B in the polyurethane contained
in the polyurethane water dispersion is not particularly limited
and is preferably from 30 to 75% by mass from the standpoint that
both the binding capability and the resistance to an electrolytic
solution are achieved.
[0054] The polyurethane water dispersion in the second embodiment
may be produced in a manner similar to the first embodiment.
[0055] The number average molecular weight of the polyurethane of
the polyurethane water dispersion is preferably 50,000 or more due
to the same reasons as described above. The polyurethane preferably
has a crosslinking density of from 0.01 to 0.50 per 1,000 molecular
weight of the polyurethane, as similar to the above. The
polyurethane preferably has a urethane bond amount of from 150 to
2,000 g/eq, and more preferably from 200 to 1,000 g/eq, as similar
to the above. The polyurethane preferably has a urea bond amount of
from 300 to 20,000 g/eq, and more preferably from 400 to 10,000
g/eq, as similar to the above.
[0056] In still another (third) embodiment of the invention, the
binder for an electrode contains an aqueous resin composition
containing a polymer of an unsaturated polymerizable monomer that
is emulsified with the hydrophilic group-containing
polyurethane.
[0057] The polymer of an unsaturated polymerizable monomer is not
particularly limited as far as it is constituted by an unsaturated
polymerizable monomer (a), and examples of the unsaturated
polymerizable monomer (a) include a carboxylic acid
group-containing unsaturated polymerizable monomer, and an alkyl
ester and a vinyl compound of a carboxylic acid group-containing
unsaturated polymerizable monomer.
[0058] Examples of the carboxylic acid group-containing unsaturated
polymerizable monomer include (meth)acrylic acid, which includes
methacrylic acid, crotonic acid, maleic acid and itaconic acid.
Examples of the alkyl ester of a carboxylic acid group-containing
unsaturated polymerizable monomer include a mono(meth)acrylate
ester, such as methyl(meth)acrylate, ethyl(meth)acrylate,
propyl(meth)acrylate, isopropyl(meth)acrylate, butyl(meth)acrylate,
n-butyl(meth)acrylate, isobutyl(meth)acrylate, hexyl(meth)acrylate,
2-ethylhexyl(meth)acrylate, octyl(meth)acrylate,
nonyl(meth)acrylate, decyl(meth)acrylate, stearyl(meth)acrylate,
isostearyl(meth)acrylate, lauryl(meth)acrylate,
cyclohexyl(meth)acrylate, t-butylcyclohexyl(meth)acrylate,
isobornyl(meth)acrylate, adamantyl(meth)acrylate,
bicyclo[3,3,1]nonyl(meth)acrylate, 2-methoxyethyl(meth)acrylate,
tetrahydrofurfuryl(meth)acrylate, benzyl(meth)acrylate,
allyl(meth)acrylate, diethylaminoethyl(meth)acrylate,
2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,
3-hydroxypropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate,
methoxyethylene glycol(meth)acrylate, methoxypolyethylene
glycol(meth)acrylate, ethoxyethylene glycol(meth)acrylate,
ethoxypolyethylene glycol(meth)acrylate, propoxyethylene
glycol(meth)acrylate, propoxypolyethylene glycol(meth)acrylate,
methoxypropylene glycol(meth)acrylate, methoxypolypropylene
glycol(meth)acrylate, ethoxypropylene glycol(meth)acrylate,
ethoxypolypropylene glycol(meth)acrylate, propoxypropylene
glycol(meth)acrylate, propoxypolypropylene glycol(meth)acrylate and
phenoxyethylene glycol(meth)acrylate, a di(meth)acrylate compound,
such as ethylene glycol di(meth)acrylate, polyethylene glycol
di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene
glycol di(meth)acrylate and triethylene glycol di(meth)acrylate, a
tri(meth)acrylate compound, such as trimethylolpropane
tri(meth)acrylate and glycerin tri(meth)acrylate, a
tetra(meth)acrylate compound, such as pentaerythritol
tetra(meth)acrylate, and a hexa(meth)acrylate compound, such as
sorbitol hexa(meth)acrylate. Examples of the vinyl compound of a
carboxylic acid group-containing unsaturated polymerizable monomer
include vinyl acetate, vinyl propionate and
2-(meth)acryloyloxyethyl phthalate. Other examples of the
unsaturated polymerizable monomer include styrene,
.alpha.-methylstyrene, vinyltoluene, acrylonitrile,
methacrylonitrile, butadiene and isoprene. The unsaturated
polymerizable monomers (a) may be used solely or as a combination
of two or more kinds thereof. In the unsaturated polymerizable
monomers (a), methyl(meth)acrylate, phenoxyethylene
glycol(meth)acrylate, styrene and butadiene are preferred from the
standpoint of the influence on the resistance to an electrolytic
solution and the raw material cost.
[0059] In the polymerization of the unsaturated polymerizable
monomer (a), polymerization reaction may be performed by adding a
known polymerization initiator (c). Examples of the polymerization
initiator (c) used include an azo initiator, such as
2,2'-asobisisobutyronitrile,
2,2'-azobis(2-methylpropionamidine)disulfate,
2,2'-azobis(2-amidinopropane)dihydrochloride,
2,2'-azobis(2-(5-methyl-2-imidazolin-2-yl)propane)dihydrochloride
and 2,2'-azobis(N,N'-dimethyleneisobutylamidine); and a substituted
ethane initiator, such as phenyl-substituted ethane. Examples
thereof used also include a redox initiator obtained by combination
of a peroxide initiator, such as a persulfate salt, such as
potassium persulfate, sodium persulfate and ammonium persulfate,
and a peroxide, such as hydrogen peroxide, t-butylhydro peroxide,
and cumene hydroperoxide, and a reducing agent, such as a sulfite
salt, such as sodium sulfite, a hydrogen sulfate salt, such as
sodium hydrogen sulfate, a metal salt, such as cuprous sulfate and
ferrous sulfate, and an organic reducing agent, such as L-ascorbic
acid.
[0060] The polymerization method utilized therefor may be known
emulsion polymerization. The polymerization temperature may be
controlled depending on the species of the polymerization
initiator, and is preferably, for example, from 20 to 100.degree.
C. The amount of the polymerization initiator (c) used is generally
suitably from 0.005 to 1 part by mass per 100 parts by mass of the
unsaturated polymerizable monomer (a).
[0061] In the polymerization of the unsaturated polymerizable
monomer (a), an emulsifier for emulsion polymerization may be used
in combination. Examples of the emulsifier for emulsion
polymerization include an unreactive one and a reactive one, and
examples of each of them include anionic, nonionic and cationic
emulsifiers for emulsion polymerization. The emulsifier may be
appropriately selected depending on the species of the hydrophilic
group of the hydrophilic group-containing polyurethane. The anionic
reactive surfactant used in the invention is not particularly
limited, and specific examples thereof include Adecalia Soap SR-10,
SR-20 and SE-10N (produced by Adeka Corporation), Aqualon HS-10,
HS-20, KH-05 and KH-10 (produced by Dai-ichi Kogyo Seiyaku Co.,
Ltd.), Eleminol JS-2 (produced by Sanyo Chemical Industries, Ltd.),
and Latemul PD-104 (produced by Kao Corporation). The nonionic
reactive surfactant used in the invention is not particularly
limited, and specific examples thereof include Adekasoap ER-10 and
ER-20 (produced by Adeka Corporation), Aqualon RN-10, RN-20, RN-30
and RN-50 (produced by Dai-ichi Kogyo Seiyaku Co., Ltd.), and
Latemul PD-420 and PD-430 (produced by Kao Corporation).
[0062] The hydrophilic group-containing polyurethane used in the
invention is formed of (A) the polyisocyanate, (B) the compound
that has two or more active hydrogen groups, (C) the compound that
has one or more active hydrogen groups and one or more hydrophilic
groups, and (D) the chain extending agent, as similar to the first
and second embodiments.
[0063] (A) The polyisocyanate is not particularly limited as
similar to the first and second embodiments, and polyisocyanates
that are ordinarily used in this field of art may be used. Specific
examples thereof include those described for the first embodiment,
and preferred examples thereof are also the same. They may be used
solely or as a combination of two or more kinds thereof. The
preferred content thereof is also the same as above.
[0064] The component B is not particularly limited, and a wide
range of compounds that have two or more hydroxyl groups, amino
groups or mercapto groups at a molecular terminal or in a molecule
may be used. Specific examples thereof include those described for
the second embodiment, and preferred examples thereof are also the
same. The compounds may be used solely or as a combination of two
or more kinds thereof.
[0065] The component B preferably contains a polycarbonate polyol,
a polyester polyol having an aromatic ring, and/or a polyether
polyol having an aromatic ring. Specific examples thereof include
those described for the second embodiment, and preferred examples
thereof are also the same. The compounds may be used solely or as a
combination of two or more kinds thereof.
[0066] The number average molecular weight of the component B is
not particularly limited and is preferably 50 or more and 5,000 or
less. The content of the component B in the polyurethane contained
in the polyurethane water dispersion is not particularly limited
and is preferably from 40 to 75% by mass from the standpoint that
both the binding capability and the resistance to an electrolytic
solution are achieved.
[0067] The compound that has one or more hydrophilic groups and one
or more active hydrogen groups as the component C used in the
invention may be the same as those exemplified for the first
embodiment, and the compounds may be used solely or as a
combination of two or more kinds thereof. The preferred content of
the component C is also the same as above.
[0068] The chain extending agent as the component D used may be, as
similar to the above, chain extending agents that are ordinarily
used in this field of art, and among them, a diamine and a
polyamine described above are preferably used.
[0069] The number average molecular weight of the polyurethane of
the polyurethane water dispersion of the invention is preferably
50,000 or more due to the same reasons as described above.
[0070] The production method of the aqueous resin composition in
the invention is not particularly limited, and the aqueous resin
composition may be produced, for example, in the following manner.
The compound (B) that has two or more active hydrogen groups, the
compound (C) that has one or more active hydrogen groups and one or
more hydrophilic groups, and the chain extending agent (D) are
reacted with the polyisocyanate (A) in an amount that is
stoichiometrically excessive to the total amount of the active
hydrogen group contained in the components B, C and D (where the
equivalent ratio of the isocyanate group and the reactive
functional group is preferably from 1/0.85 to 1/1.1) without a
solvent or in an organic solvent having no active hydrogen group to
synthesize a urethane prepolymer having an isocyanate terminal, and
after neutralizing or quaternarizing the anionic hydrophilic group
or the cationic hydrophilic group of the component C depending on
necessity, an unsaturated polymerizable monomer is added thereto,
and then the prepolymer is emulsified in water. Thereafter, (D) the
chain extending agent in an equivalent amount that is smaller than
that of the residual isocyanate group (where the equivalent ratio
of the isocyanate group and the chain extending agent is preferably
from 1/0.5 to 1/0.9) is added thereto, and the isocyanate group in
the emulsion micelle and (D) the chain extending agent are
subjected to interfacial polymerization to form a urea bond.
Simultaneously with the chain extension or after the chain
extension, the unsaturated polymerizable monomer is polymerized to
form a polymer of an unsaturated polymerizable monomer, and the
organic solvent is distilled off under reduced pressure, thereby
producing the aqueous resin composition containing the polymer of
an unsaturated polymerizable monomer of the invention that is
emulsified with the hydrophilic group-containing polyurethane of
the invention. The chain extension may be performed with water
molecules present in the system on dispersing and emulsifying in
water, without the use of the polyamine or the like as the
component D.
[0071] The aqueous resin composition of the invention preferably
has a mass ratio (X)/(Y) of the polymer of an unsaturated
polymerizable monomer (X) and the hydrophilic group-containing
polyurethane (Y) of from 90/10 to 1/99, and more preferably from
80/20 to 10/90.
[0072] In the synthesis of the urethane prepolymer, such a solvent
may be used that is inactive to an isocyanate group and is capable
of dissolving the urethane prepolymer thus formed. Examples of the
solvent include dioxane, methyl ethyl ketone, dimethylformamide,
tetrahydrofuran, N-methyl-2-pyrrolidine, toluene and propylene
glycol monomethyl ether acetate. The solvent used in the reaction
is preferably removed finally.
[0073] The crosslinking density of the hydrophilic group-containing
polyurethane used in the invention may be obtained in a manner
similar to above, and is preferably from 0.01 to 0.50 per 1,000
molecular weight of the polyurethane due to the same reasons as
above.
[0074] The urethane bond amount of the hydrophilic group-containing
polyurethane is preferably from 150 to 2,000 g/eq, and more
preferably from 200 to 1,000 g/eq, due to the same reasons as
above.
[0075] The lithium secondary battery of the invention will be
described. A positive electrode and a negative electrode used in
the lithium secondary battery of the invention each are constituted
by an electrode active substance, a conductive agent, a collector
for the electrode active substance, a binder for binding the
electrode active substance and the conductive agent to the
collector, and the like.
[0076] The lithium secondary battery of the invention is
constituted of an electrode that is produced by using a binder
containing the polyurethane water dispersion or the aqueous resin
composition of the invention. The binder may be used in both a
positive electrode and a negative electrode.
[0077] In the lithium secondary battery of the invention, the
binder for an electrode that does not use the polyurethane water
dispersion or the aqueous resin composition may be such polymers as
polyvinylidene fluoride, a copolymer resin, such as a copolymer of
polyvinylidene fluoride with one or more of hexafluoropropylene,
perfluoromethyl vinyl ether and tetrafluoroethylene, a fluorine
resin, such as polytetrafluoroethylene and fluorine rubber, and
styrene-butadiene rubber, ethylene propylene rubber, and a
styrene-acrylonitrile copolymer, but is not limited thereto.
[0078] The positive electrode active substance used in the positive
electrode of the lithium secondary battery of the invention is not
particularly limited as far as it can perform occlusion and release
of lithium ion. Examples thereof include a metal oxide, such as
CuO, Cu.sub.2O, MnO.sub.2, MoO.sub.3, V.sub.2O.sub.5, CrO.sub.3,
MoO.sub.3, Fe.sub.2O.sub.3, Ni.sub.2O.sub.3 and CoO.sub.3, a
composite oxide of lithium and a transition metal, such as
Li.sub.xCoO.sub.2, Li.sub.xNiO.sub.2, Li.sub.xMn.sub.2O.sub.4 and
LiFePO.sub.4, a metal chalcogen compound, such as TiS.sub.2,
MoS.sub.2 and NbSe.sub.3, and a conductive polymer compound, such
as polyacene, poly-p-phenylene, polypyrrole and polyaniline. Among
these, a composite oxide of at least one selected from transition
metals including cobalt, nickel, manganese and the like with
lithium, which is generally referred to as a high voltage system,
is preferred since the releasing property of lithium ion and a high
voltage may be easily obtained. Specific examples of the composite
oxide of cobalt, nickel and manganese with lithium include
LiCoO.sub.2, LiMnO.sub.2, LiMn.sub.2O.sub.4, LiNiO.sub.2,
LiNi.sub.xCo.sub.(1-x)O.sub.2 and LiMn.sub.aNi.sub.bCo.sub.c
(wherein a+b+c=1). Materials obtained by doping the lithium
composite oxides with a small amount of an element, such as
fluorine, boron, aluminum, chromium, zirconium, molybdenum and
iron, and the lithium composite oxide in which the particles have a
surface treated with carbon, MgO, Al.sub.2O.sub.3, SiO.sub.2 or the
like may be used. The positive electrode active substance may be
used as a combination of two or more kinds thereof.
[0079] The negative electrode active substance used in the negative
electrode of the invention may be any known active substance that
is capable of performing occlusion and release of lithium ion
without particular limitation. Examples thereof used include a
carbon material, such as natural graphite, artificial graphite,
non-graphitizable carbon and graphitizable carbon. Examples thereof
used also include a metal material, such as metal lithium, an alloy
and a tin compound, a lithium transition metal nitride, a
crystalline metal oxide, an amorphous metal oxide, a silicon
compound, and a conductive polymer, and specific examples thereof
include Li.sub.4Ti.sub.5O.sub.12 and NiSi.sub.5C.sub.6.
[0080] A conductive agent is used in the positive electrode and the
negative electrode of the lithium secondary battery of the
invention. Any electronic conductive material that does not
adversely affect the battery capability may be used as the
conductive agent without particular limitation. In general, carbon
black, such as acetylene black and Ketjen black, is used, and such
conductive materials may be used as natural graphite (e.g.,
squamous graphite, scaly graphite and earthy graphite), artificial
graphite, carbon whiskers, carbon fibers, metal powder (e.g.,
copper, nickel, aluminum, silver and gold), metal fibers and a
conductive ceramic material. These may be used as a mixture of two
or more kinds thereof. The amount thereof added is preferably from
0.1 to 30% by mass, and particularly preferably from 0.2 to 20% by
mass, based on the amount of the active substance.
[0081] As the collector for the electrode active substance of the
lithium secondary battery of the invention, any electronic
conductive material that does not adversely affect the battery thus
fabricated may be used. Examples of the collector for the positive
electrode include aluminum, titanium, stainless steel, nickel,
sintered carbon, a conductive polymer and conductive glass, and
also include a material containing aluminum, copper or the like
having a surface treated with carbon, nickel, titanium, silver or
the like for enhancing the adhesion property, the conductivity, and
the oxidation resistance. Examples of the collector for the
negative electrode include copper, stainless steel, nickel,
aluminum, titanium, sintered carbon, a conductive polymer,
conductive glass and an Al--Cd alloy, and also include a material
containing copper or the like having a surface treated with carbon,
nickel, titanium, silver or the like for enhancing the adhesion
property, the conductivity, and the oxidation resistance. The
surface of the material for the collector may be subjected to an
oxidation treatment. Examples of the shape thereof include a foil
form, and also include a film form, a sheet form, a net form, a
punched or expanded member, a lath member, and a molded member,
such as a porous member and a foamed member. The thickness thereof
is not particularly limited, and may be generally from 1 to 100
.mu.m.
[0082] The electrode of the lithium secondary battery of the
invention may be produced in such a manner that the electrode
active substance, a conductive agent, and a binder for binding the
electrode active substance and the conductive agent to the
collector, and the like are mixed to form an electrode material in
a slurry form, which is coated on an aluminum foil, a copper foil
or the like as a collector, followed by evaporating the dispersion
medium.
[0083] The electrode material of the invention may contain a
thickener, such as a water soluble polymer, as a viscosity
controlling agent for forming the slurry. Specifically, one or more
kinds selected from a cellulose compound, such as a carboxymethyl
cellulose salt, methyl cellulose, ethyl cellulose, hydroxymethyl
cellulose, hydroxypropyl methyl cellulose and hydroxyethyl methyl
cellulose; a polycarboxylic acid compound, such as polyacrylic acid
and sodium polyacrylate; a compound having a vinylpyrrolidone
structure, such as polyvinylpyrrolidone; polyacrylamide,
polyethylene oxide, polyvinyl alcohol, sodium alginate, xanthan
gum, carrageenan, guar gum, agar, starch and the like may be used,
and among these, a carboxymethyl cellulose salt is preferred.
[0084] The method, the order, and the like of mixing the electrode
material are not particularly limited. For example, the active
substance and the conductive agent may be mixed in advance to be
used, and for mixing in this case, a mortar, a mill mixer, a ball
mill, such as a planetary ball mill and a shaker ball mill, a
mechano-fusion and the like may be used.
[0085] The separator used in the lithium secondary battery of the
invention may be a separator that is used in an ordinary lithium
secondary battery without particular limitation, and examples
thereof include a porous resin formed of polyethylene,
polypropylene, polyolefin, polytetrafluoroethylene or the like,
ceramics, and nonwoven fabric.
[0086] The electrolytic solution used in the lithium secondary
battery of the invention may be an electrolytic solution that is
used in an ordinary lithium secondary battery, and ordinary
materials, such as an organic electrolytic solution and an ionic
liquid, may be used.
[0087] Examples of the electrolyte salt used in the lithium
secondary battery of the invention include LiPF.sub.6, LiBF.sub.4,
LiClO.sub.4, LiAsF.sub.6, LiCl, LiBr, LiCF.sub.3SO.sub.3,
LiN(CF.sub.3SO.sub.2).sub.2, LiC(CF.sub.3SO.sub.2).sub.3, LiI,
LiAlCl.sub.4, NaClO.sub.4, NaBF.sub.4 and NaI, and particularly
include an inorganic lithium salt, such as LiPF.sub.6, LiBF.sub.4,
LiClO.sub.4 and LiAsF.sub.6, and an organic lithium salt
represented by
LiN(SO.sub.2C.sub.xF.sub.2x+1)(SO.sub.2C.sub.yF.sub.2y+1), wherein
x and y each represent an integer of 0 or from 1 to 4, provided
that x+y is from 2 to 8. Specific examples of the organic lithium
salt include LiN(SO.sub.2F).sub.2,
LiN(SO.sub.2CF.sub.3)(SO.sub.2C.sub.2F.sub.5),
LiN(SO.sub.2CF.sub.3)(SO.sub.2C.sub.3F.sub.7),
LiN(SO.sub.2CF.sub.3)(SO.sub.2C.sub.4F.sub.9),
LiN(SO.sub.2C.sub.2F.sub.5).sub.2,
LiN(SO.sub.2C.sub.2F.sub.5)(SO.sub.2C.sub.3F.sub.7) and
LiN(SO.sub.2C.sub.2F.sub.5)(SO.sub.2C.sub.4F.sub.9). Among these,
the use of LiPF.sub.6, LiBF.sub.4, LiN(CF.sub.3SO.sub.2).sub.2,
LiN(SO.sub.2F).sub.2, LiN(SO.sub.2C.sub.2F.sub.5).sub.2 or the like
for the electrolyte is preferred since excellent electric
characteristics may be provided. The electrolyte salts may be used
solely or as a combination of two or more kinds thereof. The
lithium salt is generally contained in the electrolytic solution in
a concentration of from 0.1 to 2.0 mol/L, and preferably from 0.3
to 1.5 mol/L.
[0088] The organic solvent used for dissolving the electrolyte salt
of the lithium secondary battery of the invention is not
particularly limited as far as it is an organic solvent that is
used for a non-aqueous electrolytic solution in an ordinary lithium
secondary battery, and examples thereof include a carbonate
compound, a lactone compound, an ether compound, a sulfolane
compound, a dioxolane compound, a ketone compound, a nitrile
compound and a halogenated hydrocarbon compound. Specific examples
thereof include a carbonate compound, such as dimethyl carbonate,
methyl ethyl carbonate, diethyl carbonate, ethylene carbonate,
propylene carbonate, ethylene glycol dimethyl carbonate, propylene
glycol dimethyl carbonate, ethylene glycol diethyl carbonate and
vinylene carbonate, a lactone compound, such as
.gamma.-butyrolactone, an ether compound, such as dimethoxyethane,
tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and
1,4-dioxane, a sulfolane compound, such as sulfolane and
3-methylsulfolane, a dioxolane compound, such as 1,3-dioxolane, a
ketone compound, such as 4-methyl-2-pentanone, a nitrile compound,
such as acetonitrile, propionitrile, valeronitrile and
benzonitrile, a halogenated hydrocarbon compound, such as
1,2-dichloroethane, and an ionic liquid of another compound such as
methyl formate, dimethylformamide, diethylformamide,
dimethylsulfoxide, an imidazolium salt and a quaternary ammonium
salt. Mixtures of these compounds may also be used.
[0089] Among the organic solvents, at least one kind of a
non-aqueous solvent selected from the group consisting of a
carbonate compound is preferably contained for enhancing the
solubility, the dielectric constant and the viscosity of the
electrolyte.
[0090] In the case where a polymer electrolyte or a polymer gel
electrolyte is used in the lithium secondary battery of the
invention, examples thereof capable of being used include a polymer
of ether, ester, siloxane, acrylonitrile, vinylidene fluoride,
hexafluoropropylene, acrylate, methacrylate, styrene, vinyl
acetate, vinyl chloride, oxetane and the like, a polymer having a
copolymer structure thereof, and a crosslinked material thereof,
which are polymer compounds, and the polymers may be used solely or
as a combination of two or more kinds thereof. The polymer
structure is not particularly limited, and a polymer having an
ether structure, such as polyethylene oxide, is particularly
preferred.
[0091] In the lithium secondary battery of the invention contains,
an electrolytic solution, for a liquid battery; a precursor
solution containing a polymer dissolved in an electrolytic
solution, for a gel battery; or a pre-crosslinked polymer having an
electrolyte salt dissolved therein, for a solid electrolyte
battery, is housed in a battery container.
[0092] The lithium secondary battery of the invention may have a
cylindrical shape, a coin shape, a rectangular shape or any
arbitrary shape. The basic structure of the battery is the same
regardless of the shape, and the design may be changed depending on
the purpose. In the case of producing a cylindrical battery, for
example, a negative electrode containing a negative electrode
collector having coated thereon a negative electrode active
substance and a positive electrode containing a positive electrode
collector having coated thereon a positive electrode active
substance are wound with a separator intervening therebetween to
form a wound assembly, which is then housed in a battery canister,
and a non-aqueous electrolytic solution is charged therein,
followed by sealing the battery canister with insulating plates
placed on the upper and bottom ends thereof. In the case of
applying to a coin lithium secondary battery, a negative electrode
in a disk shape, a separator, a positive electrode in a disk shape,
and stainless steel plates are laminated and housed in a coin
battery canister, and a non-aqueous electrolytic solution is
charged therein, followed by sealing the battery canister.
EXAMPLE
[0093] Examples of the invention will be described along with
comparative examples, but the invention is not limited thereto. In
the following description, all "part" and "%" are based on mass
unless otherwise indicated.
Synthesis of Polyurethane Water Dispersion 1
Synthesis Example 1-1
[0094] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 100 parts by
mass of Newpol BPE-20NK (an ethylene oxide adduct of bisphenol A,
produced by Sanyo Chemical Industries, Ltd., average hydroxyl group
value: 360 mgKOH/g, number of active hydrogen group: 2), 9.5 parts
by mass of trimethylolpropane (number of active hydrogen group: 3),
16.3 parts by mass of dimethylolpropionic acid (number of active
hydrogen group: 2), 174.2 parts by mass of dicyclohexylmethane
diisocyanate, and 200 parts by mass of methyl ethyl ketone were
placed, and reacted at 75.degree. C. for 4 hours to provide a
methyl ethyl ketone solution of a urethane prepolymer having a free
isocyanate group content of 4.2% with respect to the nonvolatile
component. The solution was cooled to 45.degree. C. and neutralized
by adding 12.3 parts by mass of triethylamine, and then the
solution was emulsified and dispersed with a homogenizer while
gradually adding 900 parts by mass water thereto. Subsequently, an
amine aqueous solution containing 8.1 parts by mass of
ethylenediamine (number of active hydrogen group: 2) diluted with
100 parts by mass of water was added thereto, and chain extending
reaction was performed for 1 hour. The solvent was removed by
heating to 50.degree. C. under reduced pressure, thereby providing
a polyurethane water dispersion 1A having a nonvolatile content of
approximately 30%.
Synthesis Example 1-2
[0095] A polyurethane water dispersion 1B having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-1 except that 100 parts by mass of Newpol
BPE-20NK was changed to 145.2 parts by mass of Kuraray Polyol
P-1020 (polyester polyol formed of 3-methyl-1,5-pentanediol and
terephthalic acid, produced by Kuraray Co., Ltd., average hydroxyl
group value: 110 mgKOH/g, number of active hydrogen group: 2), the
amount of dicyclohexylmethane diisocyanate added was changed to
129.0 parts by mass, and the amount of ethylene diamine (number of
active hydrogen group: 2) added was changed to 6.2 parts by
mass.
Synthesis Example 1-3
[0096] A polyurethane water dispersion 1C having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-1 except that 100 parts by mass of Newpol
BPE-20NK was changed to 169.2 parts by mass of PCDL T-4671
(polycarbonate polyol formed of 1,4-butanediol and 1,6-hexanediol
as constitutional components, produced by Asahi Kasei Chemicals
Corporation, average hydroxyl group value: 110 mgKOH/g, number of
active hydrogen group: 2), 174.2 parts by mass of
dicyclohexylmethane diisocyanate was changed to 105 parts by mass
of isophorone diisocyanate, and 8.1 parts by mass of ethylene
diamine (number of active hydrogen group: 2) was changed to 4.4
parts by mass of diethylenetriamine (number of active hydrogen
group: 3).
Synthesis Example 1-4
[0097] A polyurethane water dispersion 1D having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-1 except that 100 parts by mass of Newpol
BPE-20NK was changed to 145.2 parts by mass of PCDL T-4671 (number
of active hydrogen group: 2), the amount of dicyclohexylmethane
diisocyanate added was changed to 129 parts by mass, and the amount
of ethylene diamine (number of active hydrogen group: 2) added was
changed to 6.2 parts by mass.
Synthesis Example 1-5
[0098] A polyurethane water dispersion 1E having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-4 except that the amount of PCDL T-4671 added
was changed to 161.7 parts by mass, 129 parts by mass of
dicyclohexylmethane diisocyanate was changed to 112.5 parts by mass
of isophorone diisocyanate, and 6.2 parts by mass of ethylene
diamine (number of active hydrogen group: 2) was changed to 14.0
parts by mass of m-xylenediamine (number of active hydrogen group:
2).
Synthesis Example 1-6
[0099] A polyurethane water dispersion 1F having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-5 except that 14.0 parts by mass of
m-xylenediamine (number of active hydrogen group: 2) was changed to
20.3 parts by mass of 4,4'-diaminodiphenylmethane (number of active
hydrogen group: 2).
Synthesis Example 1-7
[0100] A polyurethane water dispersion 1G having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-1 except that 100 parts by mass of Newpol
BPE-20NK was changed to 141.9 parts by mass of Eternacoll UM-90
(1/3) (a polycarbonate polyol formed of 1,6-hexanediol and
1,4-cyclohexanedimethanol as constitutional components, produced by
Ube Industries, Ltd., average hydroxyl group value: 125 mgKOH/g,
number of active hydrogen group: 2), the amount of
dicyclohexylmethane diisocyanate added was changed to 132.3 parts
by mass, and the amount of ethylene diamine (number of active
hydrogen group: 2) added was changed to 6.2 parts by mass.
Synthesis Example 1-8
[0101] A polyurethane water dispersion 1H having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-1 except that 100 parts by mass of Newpol
BPE-20NK was changed to 145.2 parts by mass of Kuraray Polyol
C-1065N (polycarbonate polyol formed of 1,9-nonanediol and
2-methyl-1,8-octanediol as constitutional components, produced by
Kuraray Co., Ltd., average hydroxyl group value: 110 mgKOH/g,
number of active hydrogen group: 2), the amount of
dicyclohexylmethane diisocyanate added was changed to 129 parts by
mass, and 8.1 parts by mass of ethylene diamine (number of active
hydrogen group: 2) was changed to 18.0 parts by mass of isophorone
diamine (number of active hydrogen group: 2).
Synthesis Example 1-9
[0102] A polyurethane water dispersion 1I having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-4 except that the amount of triethylamine added
was changed to 4.9 parts by mass.
Synthesis Example 1-10
[0103] A polyurethane water dispersion 1J having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-9 except that the amount of PCDL T-4671 (number
of active hydrogen group: 2) added was changed to 127 parts by
mass, the amount of dimethylolpropionic acid (number of active
hydrogen group: 2) added was changed to 24 parts by mass, the
amount of dicyclohexylmethane diisocyanate added was changed to
139.5 parts by mass, and the amount of triethylamine added was
changed to 18.1 parts by mass.
Synthesis Example 1-11
[0104] A polyurethane water dispersion 1K having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-9 except that the amount of PCDL T-4671 (number
of active hydrogen group: 2) added was changed to 187.2 parts by
mass, 129 parts by mass of dicyclohexylmethane diisocyanate was
changed to 87 parts by mass tolylene diisocyanate, and the chain
extension reaction with ethylenediamine was changed to chain
extension reaction with water (number of active hydrogen group:
2).
Synthesis Example 1-12
[0105] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 147.0 parts
by mass of Kuraray Polyol P-1020 (number of active hydrogen group:
2), 9.5 parts by mass of trimethylolpropane (number of active
hydrogen group: 3), 14.5 parts by mass of N-methyldiethanolamine
(number of active hydrogen group: 2), 129.0 parts by mass of
dicyclohexylmethane diisocyanate, and 200 parts by mass of methyl
ethyl ketone were placed, and reacted at 75.degree. C. for 4 hours
to provide a methyl ethyl ketone solution of a urethane prepolymer
having a free isocyanate group content of 3.2% with respect to the
nonvolatile component.
[0106] The solution was then cooled to 45.degree. C. and
quaternarized by adding 15.3 parts by mass of dimethyl sulfate, and
then the solution was emulsified and dispersed with a homogenizer
while gradually adding 900 parts by mass of water thereto, thereby
performing chain extending reaction with water (number of active
hydrogen group: 2) for 1 hour. The solvent was removed by heating
to 50.degree. C. under reduced pressure, thereby providing a
polyurethane water dispersion 1L having a nonvolatile content of
approximately 30%.
Synthesis Example 1-13
[0107] A polyurethane water dispersion 1M having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-12 except that 147.0 parts by mass of Kuraray
Polyol P-1020 was changed to 147.0 parts by mass of PCDL T-4671
(number of active hydrogen group: 2), and the chain extension
reaction with water (number of active hydrogen group: 2) was
changed to chain extension reaction with 6.2 parts by mass of
ethylenediamine (number of active hydrogen group: 2).
Synthesis Example 1-14
[0108] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 206.2 parts
by mass of Poly THF1000 (polytetramethylene ether glycol, produced
by BASF AG, average hydroxyl group value: 110 mgKOH/g, number of
active hydrogen group: 2), 5.5 parts by mass of
1,4-cyclohexanedimethanol (number of active hydrogen group: 2),
16.3 parts by mass of dimethylolpropionic acid (number of active
hydrogen group: 2), 72 parts by mass of hexamethylene diisocyanate,
and 200 parts by mass of methyl ethyl ketone were placed, and
reacted at 75.degree. C. for 4 hours to provide a methyl ethyl
ketone solution of a urethane prepolymer having a free isocyanate
group content of 1.6% with respect to the nonvolatile component.
The solution was cooled to 45.degree. C. and neutralized by adding
12.3 parts by mass of triethylamine, and then the solution was
emulsified and dispersed with a homogenizer while gradually adding
900 parts by mass of water thereto. Subsequently, chain extending
reaction was performed with water (number of active hydrogen group:
2) for 1 hour. The solvent was removed by heating to 50.degree. C.
under reduced pressure, thereby providing a polyurethane water
dispersion 1N having a nonvolatile content of approximately
30%.
Synthesis Example 1-15
[0109] A polyurethane water dispersion 10 having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-14 except that 206.2 parts by mass of Poly THF
1000 was changed to 181.7 parts by mass of Kuraray Polyol P-1010
(polyester polyol formed of 3-methyl-1,5-pentanediol and adipic
acid, produced by Kuraray Co., Ltd., average hydroxyl group value:
110 mgKOH/g, number of active hydrogen group: 2), 5.5 parts by mass
of 1,4-cyclohexanedimethanol was changed to 9.5 parts by mass of
trimethylolpropane (number of active hydrogen group: 3), the amount
of hexamethylene diisocyanate was changed to 92.5 parts by mass,
and the chain extension reaction with water was changed to a chain
extending reaction with 7.8 parts by mass of diethylenetriamine
(number of active hydrogen group: 3).
Synthesis Example 1-16
[0110] A polyurethane water dispersion 1P having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 1-15 except that the amount of Kuraray Polyol
P-1010 added was changed to 212.9 parts by mass, the amount of
trimethylolpropane added was changed to 0.3 part by mass, the
amount of hexamethylene diisocyanate added was changed to 70.5
parts by mass, and the chain extension reaction with
diethylenetriamine was changed to a chain extension reaction with
water.
Evaluation of Polyurethane Water Dispersion
[0111] The free isocyanate group contents with respect to the
nonvolatile component of the methyl ethyl ketone solutions of the
urethane prepolymers thus synthesized in the synthesis examples are
shown in Table 1 below.
[0112] The mass of the nonvolatile content of the polyurethane
water dispersion thus obtained was measured according to JIS K6828.
The polyurethane water dispersions were subjected to the following
measurements. The results are shown in Table 1.
[0113] The crosslinking density of the resin solid content of the
polyurethane water dispersion was calculated by the expression 1
shown above.
[0114] The acid value, the amine value, the amount of urethane
bond, and the amount of urea bond of the polyurethane were
calculated from the charged amounts in the synthesis of the
urethane resin and the free isocyanate group content with respect
to the nonvolatile content after the reaction.
[0115] The total content of the aromatic ring and the alicyclic
ring in the polyurethane was calculated from the charged amounts in
the synthesis of the urethane resin and the charged amount of the
amine chain extending agent.
[0116] The average particle diameter of the polyurethane water
dispersion was measured with Microtrac UPA-UZ152 (produced by
Nikkiso Co., Ltd.), and the 50% average value was designated as the
average particle diameter.
TABLE-US-00001 TABLE 1 Free isocyanate Average Amount of Content of
Polyurethane group particle Acid value or urethane Amount of
aromatic ring or water content Crosslinking diameter amine value
bond urea bond alicyclic ring dispersion (%) density (.mu.m)
(mgKOH/g) (g/eq) (g/eq) (wt %) 1A 4.2 0.23 0.02 23 291 1,062 48 1B
3.3 0.23 0.02 23 398 1,372 40 1C 2.0 0.38 0.02 23 373 2,221 13 1D
3.3 0.23 0.02 23 398 1,372 26 1E 3.2 0.23 0.02 23 381 1,404 19 1F
3.2 0.23 0.02 23 381 1,404 25 1G 3.3 0.23 0.02 23 385 1,371 31 1H
3.3 0.23 0.02 23 398 1,372 31 1I 3.3 0.23 0.45 23 398 1,372 26 1J
3.3 0.23 0.01 23 398 1,372 28 1K 2.3 0.23 0.02 23 357 3,739 17 1L
3.2 0.23 0.02 23 396 1,470 40 1M 3.2 0.23 0.02 23 396 2,646 26 1N
1.6 0 0.02 23 403 5,296 0 1O 3.8 0.92 0.02 23 362 1,162 0 1P 2.2
0.007 0.02 23 436 3,955 0
Production of Electrodes
[0117] Negative electrodes and positive electrodes were produced in
the following manner by using the polyurethane water dispersions
shown in Table 2 below as a binder.
TABLE-US-00002 TABLE 2 Kind of electrode Kind of binder negative
electrode 1-1 polyurethane water dispersion 1A negative electrode
1-2 polyurethane water dispersion 1B negative electrode 1-3
polyurethane water dispersion 1C negative electrode 1-4
polyurethane water dispersion 1D negative electrode 1-5
polyurethane water dispersion 1E negative electrode 1-6
polyurethane water dispersion 1F negative electrode 1-7
polyurethane water dispersion 1G negative electrode 1-8
polyurethane water dispersion 1H negative electrode 1-9
polyurethane water dispersion 1I negative electrode 1-10
polyurethane water dispersion 1J negative electrode 1-11
polyurethane water dispersion 1K negative electrode 1-12
polyurethane water dispersion 1L negative electrode 1-13
polyurethane water dispersion 1M negative electrode 1-14
polyurethane water dispersion 1N negative electrode 1-15
polyurethane water dispersion 1O negative electrode 1-16
polyurethane water dispersion 1P negative electrode 1-17 SBR
negative electrode 1-18 polyurethane water dispersion 1A negative
electrode 1-19 SBR negative electrode 1-20 polyurethane water
dispersion 1H negative electrode 1-21 SBR negative electrode 1-22
polyurethane water dispersion 1I + crosslinking agent positive
electrode 1-1 polyvinylidene fluoride positive electrode 1-2
polyurethane water dispersion 1A positive electrode 1-3
polyurethane water dispersion 1Q positive electrode 1-4
polyvinylidene fluoride positive electrode 1-5 polyurethane water
dispersion 1H positive electrode 1-6 polyvinylidene fluoride
positive electrode 1-7 polyurethane water dispersion 1I
Negative Electrode 1-1
[0118] With a planetary mixer, 100 g of natural graphite as a
negative electrode active substance, 0.5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 2% by mass aqueous solution of carboxymethyl
cellulose (CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku
Co., Ltd.) as a thickener, and 6.7 g of a 30% by mass solution of
the polyurethane water dispersion 1A as a binder were mixed to
prepare a negative electrode slurry having a solid content of 50%.
The negative electrode slurry was coated on an electrolytic copper
foil having a thickness of 10 .mu.m with a coating machine, dried
at 120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode 1-1 having a negative
electrode active substance in an amount of 7 mg/cm.sup.2.
Negative Electrodes 1-2 to 1-11 and 1-14 to 1-17
[0119] Negative electrodes were produced in the same manner as in
the negative electrode 1-1 except that the polyurethane water
dispersion 1 A was changed to the polyurethane water dispersions or
a styrene-butadiene rubber (SBR) latex shown in Table 2.
Negative Electrodes 1-12 and 1-13
[0120] With a planetary mixer, 100 g of natural graphite as a
negative electrode active substance, 0.5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 1% by mass aqueous solution of hydroxyethyl
cellulose (HEC) (HEC Daicel SP900, produced by Daicel Chemical
Industries, Ltd.) as a thickener, and 6.7 g of a 30% by mass
solution of the polyurethane water dispersion shown in Table 2 as a
binder were mixed to prepare a negative electrode slurry having a
solid content of 50%. The negative electrode slurry was coated on
an electrolytic copper foil having a thickness of 10 .mu.m with a
coating machine, dried at 120.degree. C., and then subjected to a
roll pressing treatment, thereby providing a negative electrode
having a negative electrode active substance in an amount of 7
mg/cm.sup.2.
Negative Electrode 1-18
[0121] With a planetary mixer, 100 g of SiO (average particle
diameter: 4.5 .mu.m, specific surface area: 5.5 m.sup.2/g) as a
negative electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent,
100 g of a 2% by mass aqueous solution of carboxymethyl cellulose
(CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.)
as a thickener, and 6.7 g of a 30% by mass solution of the
polyurethane water dispersion 1A as a binder were mixed to prepare
a negative electrode slurry having a solid content of 50%. The
negative electrode slurry was coated on an electrolytic copper foil
having a thickness of 10 .mu.m with a coating machine, dried at
120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode having a negative electrode
active substance in an amount of 2.5 mg/cm.sup.2.
Negative Electrode 1-19
[0122] A negative electrode was produced in the same manner as in
the negative electrode 1-18 except that the polyurethane water
dispersion 1A was changed to an SBR latex.
Negative Electrode 1-20
[0123] With a planetary mixer, 100 g of Li.sub.4Ti.sub.5O.sub.12 as
a negative electrode active substance, 5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 2% by mass aqueous solution of carboxymethyl
cellulose (CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku
Co., Ltd.) as a thickener, and 6.7 g of a 30% by mass solution of
the polyurethane water dispersion 1H as a binder were mixed to
prepare a negative electrode slurry having a solid content of 50%.
The negative electrode slurry was coated on an electrolytic copper
foil having a thickness of 10 .mu.m with a coating machine, dried
at 120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode having a negative electrode
active substance in an amount of 9.7 mg/cm.sup.2.
Negative Electrode 1-21
[0124] A negative electrode was produced in the same manner as in
the negative electrode 1-20 except that the polyurethane water
dispersion 1H was changed to an SBR latex.
Negative Electrode 1-22
[0125] With a planetary mixer, 100 g of natural graphite as a
negative electrode active substance, 0.5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 2% by mass aqueous solution of carboxymethyl
cellulose (CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku
Co., Ltd.) as a thickener, and 6.7 g of a 30% by mass solution of
the polyurethane water dispersion 1I as a binder were mixed, and
then 0.1 g of a polyisocyanate crosslinking agent (Aquanate AQ-210,
produced by Nippon Polyurethane Industry Co., Ltd.) as a
crosslinking agent was added and mixed therewith to prepare a
negative electrode slurry having a solid content of 50%. The
negative electrode slurry was coated on an electrolytic copper foil
having a thickness of 10 .mu.m with a coating machine, dried at
120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode having a negative electrode
active substance in an amount of 7 mg/cm.sup.2.
Positive Electrode 1-1
[0126] With a planetary mixer, 100 g of
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 as a positive electrode
active substance, 7.8 g of carbon black (Super-P, produced by
Timcal Graphite & Carbon) as a conductive agent, 6 g of
polyvinylidene fluoride (PVDF) as a binder, and 61.3 g of
N-methyl-2-pyrrolidone as a dispersion medium were mixed to prepare
a positive electrode slurry having a solid content of 65%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 13.8 mg/cm.sup.2.
Positive Electrodes 1-2 and 1-3
[0127] With a planetary mixer, 100 g of
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 as a positive electrode
active substance, 7.8 g of carbon black (Super-P, produced by
Timcal Graphite & Carbon) as a conductive agent, 100 g of a 2%
by mass aqueous solution of carboxymethyl cellulose (Cellogen WS-C,
produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a thickener, and
6.7 g of a 30% by mass solution of the polyurethane water
dispersion shown in Table 2 as a binder were mixed to prepare a
positive electrode slurry having a solid content of 50%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 13.8 mg/cm.sup.2.
Positive Electrode 1-4
[0128] With a planetary mixer, 100 g of LiMn.sub.2O.sub.4 as a
positive electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent, 6
g of polyvinylidene fluoride as a binder, and 59.8 g of
N-methyl-2-pyrrolidone as a dispersion medium were mixed to prepare
a positive electrode slurry having a solid content of 65%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 22 mg/cm.sup.2.
Positive Electrode 1-5
[0129] With a planetary mixer, 100 g of LiMn.sub.2O.sub.4 as a
positive electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent,
100 g of a 2% by mass aqueous solution of carboxymethyl cellulose
(Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a
thickener, and 6.7 g of a 30% by mass solution of the polyurethane
water dispersion 1G as a binder were mixed to prepare a positive
electrode slurry having a solid content of 50%. The positive
electrode slurry was coated on an aluminum foil having a thickness
of 20 .mu.m with a coating machine, dried at 130.degree. C., and
then subjected to a roll pressing treatment, thereby providing a
positive electrode having a positive electrode active substance in
an amount of 22 mg/cm.sup.2.
Positive Electrode 1-6
[0130] With a planetary mixer, 100 g of LiFeOP.sub.4 as a positive
electrode active substance, 5 g of carbon black (Super-P, produced
by Timcal Graphite & Carbon) as a conductive agent, 6 g of
polyvinylidene fluoride as a binder, and 135.7 g of
N-methyl-2-pyrrolidone as a dispersion medium were mixed to prepare
a positive electrode slurry having a solid content of 45%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 14.5 mg/cm.sup.2.
Positive Electrode 1-7
[0131] With a planetary mixer, 100 g of LiFeOP.sub.4 as a positive
electrode active substance, 5 g of carbon black (Super-P, produced
by Timcal Graphite & Carbon) as a conductive agent, 100 g of a
2% by mass aqueous solution of carboxymethyl cellulose (Cellogen
WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a thickener,
and 6.7 g of a 30% by mass solution of the polyurethane water
dispersion 1H as a binder were mixed to prepare a positive
electrode slurry having a solid content of 50%. The positive
electrode slurry was coated on an aluminum foil having a thickness
of 20 .mu.m with a coating machine, dried at 130.degree. C., and
then subjected to a roll pressing treatment, thereby providing a
positive electrode having a positive electrode active substance in
an amount of 14.5 mg/cm.sup.2.
Evaluation of Electrode
[0132] The electrodes thus obtained were subjected to the following
evaluation. The evaluation results are shown in Table 3.
Evaluation of Binding Capability
[0133] The electrode thus obtained was folded by 180.degree. with
the coated surface directed outward and unfolded, and then the
extent of drop-off of the active substance on the coated surface
(the proportion of the drop-off area with respect to the total
area) was visually determined and evaluated according to the
following standard.
5: 0% drop-off 4: 25% drop-off 3: 50% drop-off 2: 75% drop-off 1:
100% drop-off
Evaluation of Resistance to Electrolytic Solution
[0134] The electrode thus obtained was immersed in a mixed solvent
containing EC (ethylene carbonate)/PC (propylene carbonate)/DMC
(dimethyl carbonate)/EMC (ethylmethyl carbonate)/DEC (diethyl
carbonate)=1/1/1/1/1 (by volume) at a liquid temperature of
60.degree. C. for 7 days, and then the appearance of the coated
film was visually observed and evaluated according to the following
standard.
A: no change found on coated film B: several blisters formed on
coated film C: drop-off of coated film found
TABLE-US-00003 TABLE 3 Evaluation of Evaluation resistance of
binding to electrolytic Kind of electrode capability solution
Example 1-1 negative electrode 1-1 4 A Example 1-2 negative
electrode 1-2 4 A Example 1-3 negative electrode 1-3 4 A Example
1-4 negative electrode 1-4 5 A Example 1-5 negative electrode 1-5 4
A Example 1-6 negative electrode 1-6 5 A Example 1-7 negative
electrode 1-7 4 A Example 1-8 negative electrode 1-8 5 A Example
1-9 negative electrode 1-9 5 A Example 1-10 negative electrode 1-10
5 A Example 1-11 negative electrode 1-11 4 A Example 1-12 negative
electrode 1-12 4 A Example 1-13 negative electrode 1-13 5 A Example
1-14 negative electrode 1-18 4 A Example 1-15 negative electrode
1-20 5 A Example 1-16 negative electrode 1-22 5 A Example 1-17
positive electrode 1-2 4 A Example 1-18 positive electrode 1-5 5 A
Example 1-19 positive electrode 1-7 5 A Comparative negative
electrode 1-17 3 A Example 1-1 Comparative negative electrode 1-19
3 A Example 1-2 Comparative negative electrode 1-21 3 A Example 1-3
Comparative positive electrode 1-1 3 A Example 1-4 Comparative
positive electrode 1-4 3 A Example 1-5 Comparative positive
electrode 1-6 3 A Example 1-6
Production of Lithium Secondary Battery
[0135] The negative electrode and the positive electrode thus
obtained were combined as shown in Table 4 below and laminated on
each other with a polyolefin (PE/PP) separator as a separator
intervening between the electrodes, and a positive electrode
terminal and a negative electrode terminal were ultrasonic-welded
to the positive and negative electrodes respectively. The laminate
was placed in an aluminum-laminated package, which was heat-sealed
except for an opening for injecting a liquid, thereby producing a
battery without a liquid injected having a positive electrode area
of 18 cm.sup.2 and a negative electrode area of 19.8 cm.sup.2. In a
solvent obtained by mixing ethylene carbonate and diethyl carbonate
(30/70 in volume), LiPF.sub.6 (1.0 mol/L) was dissolved to prepare
an electrolytic solution, which was then charged in the battery,
and the opening was heat-sealed, thereby providing a battery for
evaluation.
TABLE-US-00004 TABLE 4 Constitution of electrodes Negative
electrode Positive electrode Example 1-20 negative electrode 1-1
positive electrode 1-1 Example 1-21 negative electrode 1-2 positive
electrode 1-1 Example 1-22 negative electrode 1-3 positive
electrode 1-1 Example 1-23 negative electrode 1-4 positive
electrode 1-1 Example 1-24 negative electrode 1-5 positive
electrode 1-1 Example 1-25 negative electrode 1-6 positive
electrode 1-1 Example 1-26 negative electrode 1-7 positive
electrode 1-1 Example 1-27 negative electrode 1-8 positive
electrode 1-1 Example 1-28 negative electrode 1-9 positive
electrode 1-1 Example 1-29 negative electrode 1-10 positive
electrode 1-1 Example 1-30 negative electrode 1-11 positive
electrode 1-1 Example 1-31 negative electrode 1-12 positive
electrode 1-1 Example 1-32 negative electrode 1-13 positive
electrode 1-1 Example 1-33 negative electrode 1-18 positive
electrode 1-1 Example 1-34 negative electrode 1-20 positive
electrode 1-1 Example 1-35 negative electrode 1-22 positive
electrode 1-1 Example 1-36 negative electrode 1-17 positive
electrode 1-2 Example 1-37 negative electrode 1-17 positive
electrode 1-5 Example 1-38 negative electrode 1-17 positive
electrode 1-7 Example 1-39 negative electrode 1-7 positive
electrode 1-2 Comparative Example negative electrode 1-17 positive
electrode 1-1 1-7 Comparative Example negative electrode 1-19
positive electrode 1-1 1-8 Comparative Example negative electrode
1-21 positive electrode 1-1 1-9 Comparative Example negative
electrode 1-17 positive electrode 1-3 1-10 Comparative negative
electrode 1-17 positive electrode 1-4 Example 1-11 Comparative
negative electrode 1-17 positive electrode 1-6 Example 1-12
Evaluation of Battery Capability
[0136] The lithium secondary batteries thus produced above were
subjected to a capability test at 20.degree. C. The test method was
as follows. The test results are shown in Table 5.
Cell Impedance
[0137] For the cell impedance, a resistance value at a frequency of
1 kHz was measured with an impedance analyzer (produced by
ZAHNER-Elektrik GmbH & CoKG).
Charge and Discharge Cycle Characteristics
[0138] The charge and discharge cycle characteristics were measured
under the following condition.
[0139] In the case where LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 or
LiMn.sub.2O.sub.4 was used as the positive electrode active
substance, and natural graphite was used as the negative electrode
active substance, a cycle, in which the battery was charged at
constant current (CC) and a current density corresponding to 1 C
until 4.2 V, charged for 1.5 hours after switching to constant
voltage (CV) charging at 4.2 V, and then discharged at CC and a
current density corresponding to 1 C until 2.7 V, was performed for
300 cycles at 20.degree. C., and the ratio of the 1 C discharge
capacity after the 300 cycles with respect to the initial 1 C
discharge capacity was designated as a 1 C charge and discharge
cycle retention.
[0140] In the case where LiFeOP.sub.4 was used as the positive
electrode active substance, and natural graphite was used as the
negative electrode active substance, a cycle, in which the battery
was charged at constant current (CC) and a current density
corresponding to 1 C until 4.0 V, charged for 1.5 hours after
switching to constant voltage (CV) charging at 4.0 V, and then
discharged at CC and a current density corresponding to 1 C until
2.0 V, was performed for 300 cycles at 20.degree. C., and the ratio
of the 1 C discharge capacity after the 300 cycles with respect to
the initial 1 C discharge capacity was designated as a 1 C charge
and discharge cycle retention. In the case where
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 was used as the positive
electrode active substance, and Li.sub.4Ti.sub.5O.sub.12 was used
as the negative electrode active substance, a cycle, in which the
battery was charged at constant current (CC) and a current density
corresponding to 1 C until 2.9 V, charged for 1.5 hours after
switching to constant voltage (CV) charging at 2.9 V, and then
discharged at CC and a current density corresponding to 1 C until
1.0 V, was performed for 300 cycles at 20.degree. C., and the ratio
of the 1 C discharge capacity after the 300 cycles with respect to
the initial 1 C discharge capacity was designated as a 1 C charge
and discharge cycle retention.
[0141] In the case where LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2
was used as the positive electrode active substance, and SiO was
used as the negative electrode active substance, a cycle, in which
the battery was charged at constant current (CC) and a current
density corresponding to 1 C until 4.2 V, charged for 1.5 hours
after switching to constant voltage (CV) charging at 4.2 V, and
then discharged at CC and a current density corresponding to 1 C
until 2.7 V, was performed for 50 cycles at 20.degree. C., and the
ratio of the 1 C discharge capacity after the 50 cycles with
respect to the initial 1 C discharge capacity was designated as a 1
C charge and discharge cycle retention.
TABLE-US-00005 TABLE 5 Evaluation of battery Cell impedance
Capacity retention after charge (m.OMEGA./1 kHz) and discharge
cycles (%) Example 1-20 183 97.2 Example 1-21 197 95.3 Example 1-22
201 94.5 Example 1-23 190 96.3 Example 1-24 200 95.4 Example 1-25
202 95.0 Example 1-26 185 97.0 Example 1-27 187 96.7 Example 1-28
188 96.5 Example 1-29 196 96.0 Example 1-30 202 95.0 Example 1-31
204 94.6 Example 1-32 201 94.8 Example 1-33 205 94.3 Example 1-34
185 97.3 Example 1-35 194 95.7 Example 1-36 198 95.3 Example 1-37
200 95.1 Example 1-38 182 97.5 Example 1-39 187 97.1 Comparative
Example 230 91.1 1-7 Comparative Example 248 87.2 1-8 Comparative
Example 220 92.5 1-9 Comparative Example 290 75.8 1-10 Comparative
Example 236 90.3 1-11 Comparative Example 225 91.8 1-12
[0142] It is understood from Table 5 that as compared to the use of
styrene-butadiene rubber or polyvinylidene fluoride having been
used, the use of the polyurethane water dispersion of the invention
provides more excellent binding capability, a lower cell impedance,
and a higher capacity retention after the charge and discharge
cycles.
Synthesis of Polyurethane Water Dispersion 2
Synthesis Example 2-1
[0143] While bubbling nitrogen gas in a reaction vessel equipped
with a thermometer, a nitrogen gas introducing tube and a stirrer,
220 parts by mass of adipic acid, 180 parts by mass of
3-methyl-1,5-pentanediol and 0.1 part of tetrabutyl titanate were
charged therein, and reaction was performed at a reaction
temperature controlled to from 160 to 170.degree. C. to make an
overhead temperature of from 50 to 60.degree. C. until the acid
value reached 0.3 mgKOH/g or lower. The reaction was then performed
at 180.degree. C. under a reduced pressure condition of 5 kPaabs or
lower for 2 hours, thereby providing a polyester polyol having a
hydroxyl group value of 112 mgKOH/g and an acid value of 0.2
mgKOH/g. In the reaction vessel, furthermore, 53.4 parts of
dimethyl isophthalate 5-sodium sulfonate (DMIS) and 0.8 part of
tetrabutyl titanate were charged, and reaction was performed at a
reaction temperature controlled to from 170 to 180.degree. C. to
make an overhead temperature of from 50 to 70.degree. C., thereby
providing a sulfonic acid-containing polyester polyol (a-1) having
a hydroxyl group value of 53 mgKOH/g, an acid value of 0.3 mgKOH/g
and a number of active hydrogen group of 2.
[0144] The resulting polyol was measured for an acid value
according to JIS K1557 and for an average hydroxyl group value
according to JIS K1557.
[0145] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 184.2 parts
by mass of the polyester polyol (a-1) (number of active hydrogen
group: 2), 9.5 parts by mass of trimethylolpropane (number of
active hydrogen group: 3), 16.3 parts by mass of
1,4-cyclohexanedimethanol (number of active hydrogen group: 2), 90
parts by mass of isophorone diisocyanate, and 200 parts by mass of
methyl ethyl ketone were placed, and reacted at 75.degree. C. for 4
hours to provide a methyl ethyl ketone solution of a urethane
prepolymer having a free isocyanate group content of 2.7% with
respect to the nonvolatile component. The solution was cooled to
45.degree. C. and emulsified and dispersed with a homogenizer while
gradually adding 900 parts by mass of water thereto. Subsequently,
an amine aqueous solution containing 5.2 parts by mass of
ethylenediamine (number of active hydrogen group: 2) diluted with
100 parts by mass of water was added thereto, and chain extending
reaction was performed for 1 hour. The solvent was removed by
heating to 50.degree. C. under reduced pressure, thereby providing
a polyurethane water dispersion 2A having a nonvolatile content of
approximately 30%.
Synthesis Example 2-2
[0146] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 145 parts by
mass of Newpol BPE-20NK (an ethylene oxide adduct of bisphenol A,
produced by Sanyo Chemical Industries, Ltd., average hydroxyl group
value: 360 mgKOH/g, number of active hydrogen group: 2), 9.5 parts
by mass of trimethylolpropane (number of active hydrogen group: 3),
16.3 parts by mass of dimethylolpropionic acid (number of active
hydrogen group: 2), 129.2 parts by mass of hexamethylene
diisocyanate, and 200 parts by mass of methyl ethyl ketone were
placed, and reacted at 75.degree. C. for 4 hours to provide a
methyl ethyl ketone solution of a urethane prepolymer having a free
isocyanate group content of 3.5% with respect to the nonvolatile
component. The solution was cooled to 45.degree. C. and neutralized
by adding 12.3 parts by mass of triethylamine, and then the
solution was emulsified and dispersed with a homogenizer while
gradually adding 900 parts by mass of water thereto. Subsequently,
an amine aqueous solution containing 6.8 parts by mass of
ethylenediamine (number of active hydrogen group: 2) diluted with
100 parts by mass of water was added thereto, and chain extending
reaction was performed for 1 hour. The solvent was removed by
heating to 50.degree. C. under reduced pressure, thereby providing
a polyurethane water dispersion 2B having a nonvolatile content of
approximately 30%.
Synthesis Example 2-3
[0147] A polyurethane water dispersion 2C having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-2 except that 6.8 parts by mass of
ethylenediamine (number of active hydrogen group: 2) was changed to
15.4 parts by mass of m-xylenediamine (number of active hydrogen
group: 2).
Synthesis Example 2-4
[0148] A polyurethane water dispersion 2D having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-2 except that 6.8 parts by mass of
ethylenediamine (number of active hydrogen group: 2) was changed to
22.4 parts by mass of 4,4'-diaminodiphenylmethane (number of active
hydrogen group: 2).
Synthesis Example 2-5
[0149] A polyurethane water dispersion 2E having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-2 except that 145.0 parts by mass of Newpol
BPE-20NK and 9.5 parts by mass of trimethylolpropane were changed
to 140.7 parts by mass of Newpol BPE-20NK and 13.8 parts by mass of
1,4-cyclohexanedimethanol (number of active hydrogen group: 2), and
6.8 parts by mass of ethylenediamine was changed to 9.1 parts by
mass of diethylenetriamine (number of active hydrogen group:
3).
Synthesis Example 2-6
[0150] A polyurethane water dispersion 2F having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-2 except that 145.0 parts by mass of Newpol
BPE-20NK was changed to 60 parts by mass of Nippolan N-4009 (a
trade name, a polyester polyol formed of 1,4-butanediol and adipic
acid, produced by Nippon Polyurethane Industry Co., Ltd., average
hydroxyl group value: 112 mgKOH/g, number of active hydrogen group:
2) and 114 parts by mass of Adekapolyether BPX-11 (a trade name, a
propylene oxide adduct of bisphenol A, produced by Adeka
Corporation, average hydroxyl group value: 312 mgKOH/g, number of
active hydrogen group: 2), the amount of trimethylolpropane (number
of active hydrogen group: 3) added was changed to 5.5 parts by
mass, the amount of hexamethylene diisocyanate added was changed to
104.2 parts by mass, and the chain extension reaction with
ethylenediamine was changed to chain extension reaction with water
(number of active hydrogen group: 2).
Synthesis Example 2-7
[0151] A polyurethane water dispersion 2G having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-2 except that 145.0 parts by mass of Newpol
BPE-20NK was changed to 105.5 parts by mass of Teslac 2477 (a trade
name, a polyester polyol formed of 1,6-hexanediol, adipic acid and
isophthalic acid, produced by Hitachi Kasei Polymer Co., Ltd.,
average hydroxyl group value: 64 mgKOH/g, number of active hydrogen
group: 2) and 36.9 parts by mass of Adekapolyether BPX-11 (number
of active hydrogen group: 2), 129.2 parts by mass of hexamethylene
diisocyanate was changed to 131.8 parts by mass of
dicyclohexylmethane diisocyanate, and the amount of ethylenediamine
(number of active hydrogen group: 3) added was changed to 6.0 parts
by mass.
Synthesis Example 2-8
[0152] While bubbling nitrogen gas in a reaction vessel equipped
with a thermometer, a nitrogen gas introducing tube and a stirrer,
93.6 parts by mass of adipic acid, 106.4 parts by mass of
terephthalic acid, 220 parts by mass of neopentyl glycol, and 0.4
part by mass of tetrabutyl titanate were charged therein, and
reaction was performed at a reaction temperature controlled to from
160 to 170.degree. C. to make an overhead temperature of from 50 to
60.degree. C. for 8 hours, thereby providing a polyester polyol
(a-2) having an acid value of 0.3 mgKOH/g, an average hydroxyl
group value of 56 mgKOH/g and a number of active hydrogen group of
2.
[0153] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 187.2 parts
by mass of the polyol (a-2), 9.5 parts by mass of
trimethylolpropane (number of active hydrogen group: 3), 16.3 parts
by mass of dimethylolpropionic acid (number of active hydrogen
group: 2), 87 parts by mass of isophorone diisocyanate, and 200
parts by mass of methyl ethyl ketone were placed, and reacted at
75.degree. C. for 4 hours to provide a methyl ethyl ketone solution
of a urethane prepolymer having a free isocyanate group content of
1.9% with respect to the nonvolatile component. The solution was
cooled to 45.degree. C. and neutralized by adding 12.3 parts by
mass of triethylamine, and then the solution was emulsified and
dispersed with a homogenizer while gradually adding 900 parts by
mass of water thereto, thereby performing chain extending reaction
with water (number of active hydrogen group: 2) for 1 hour. The
solvent was removed by heating to 50.degree. C. under reduced
pressure, thereby providing a polyurethane water dispersion 2H
having a nonvolatile content of approximately 30%.
Synthesis Example 2-9
[0154] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 184.2 parts
by mass of Eternacoll UH-100 (a polycarbonate polyol formed of
1,6-hexanediol as constitutional component, produced by Ube
Industries, Ltd., average hydroxyl group value: 110 mgKOH/g, number
of active hydrogen group: 2), 9.5 parts by mass of
trimethylolpropane (number of active hydrogen group: 3), 16.3 parts
by mass of dimethylolpropionic acid (number of active hydrogen
group: 2), 90 parts by mass of diphenylmethane diisocyanate, and
200 parts by mass of methyl ethyl ketone were placed, and reacted
at 75.degree. C. for 4 hours to provide a methyl ethyl ketone
solution of a urethane prepolymer having a free isocyanate group
content of 0.2% or less with respect to the nonvolatile component.
The solution was cooled to 45.degree. C. and neutralized by adding
12.3 parts by mass of triethylamine, and then the solution was
emulsified and dispersed with a homogenizer while gradually adding
900 parts by mass of water thereto. The solvent was removed by
heating to 50.degree. C. under reduced pressure, thereby providing
a polyurethane water dispersion 21 having a nonvolatile content of
approximately 30%.
Synthesis Example 2-10
[0155] A polyurethane water dispersion 2J having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-2 except that 145.0 parts by mass of Newpol
BPE-20NK was changed to 129.2 parts by mass of URIC H-62 (a trade
name, a castor oil polyol, produced by Itoh Oil Chemicals Co.,
Ltd., average hydroxyl group value: 260 mgKOH/g, number of active
hydrogen group: 2), and 129.2 parts by mass of hexamethylene
diisocyanate was changed to 145.0 parts by mass of isophorone
diisocyanate.
Synthesis Example 2-11
[0156] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 121.0 parts
by mass of Newpol BPE-20NK, 9.5 parts by mass of
trimethylolpropane, 14.5 parts by mass of N-methyldiethanolamine,
155.0 parts by mass of isophorone diisocyanate, and 200 parts by
mass of methyl ethyl ketone were placed, and reacted at 75.degree.
C. for 4 hours to provide a methyl ethyl ketone solution of a
urethane prepolymer having a free isocyanate group content of 3.4%
with respect to the nonvolatile component. The solution was cooled
to 45.degree. C. and quaternarized by adding 15.3 parts by mass of
dimethyl sulfate, and then the solution was emulsified and
dispersed with a homogenizer while gradually adding 900 parts by
mass of water thereto, thereby performing chain extending reaction
with water (number of active hydrogen group: 2) for 1 hour. The
solvent was removed by heating to 50.degree. C. under reduced
pressure, thereby providing a polyurethane water dispersion 2K
having a nonvolatile content of approximately 30%.
Synthesis Example 2-12
[0157] A polyurethane water dispersion 2L having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-11 except that the chain extending reaction
with water (number of active hydrogen group: 2) was changed to
chain extending reaction with 6.5 parts by mass of ethylenediamine
(number of active hydrogen group: 2).
Synthesis Example 2-13
[0158] A polyurethane water dispersion 2M having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-2 except that 145 parts by mass of Newpol
BPE-20NK and 9.5 parts by mass of trimethylolpropane were changed
to 206.2 parts by mass of Nippolan N-4009 and 5.5 parts by mass of
1,4-cyclohexanedimethanol, the amount of hexamethylene diisocyanate
added was changed to 72.0 parts by mass, and the chain extending
reaction with ethylenediamine (number of active hydrogen group: 2)
was changed to chain extending reaction with water (number of
active hydrogen group: 2).
Synthesis Example 2-14
[0159] A polyurethane water dispersion 2N having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-13 except that 206.2 parts by mass of Nippolan
N-4009 was changed to 181.7 parts by mass thereof, 5.5 parts by
mass of 1,4-cyclohexanedimethanol was changed to 9.5 parts by mass
of trimethylolpropane, the amount of hexamethylene diisocyanate
added was changed to 92.5 parts by mass, and the chain extending
reaction with water (number of active hydrogen group: 2) was
changed to chain extending reaction with 7.8 parts by mass of
diethylenetriamine (number of active hydrogen group: 3).
Synthesis Example 2-15
[0160] A polyurethane water dispersion 20 having a nonvolatile
content of approximately 30% was produced in the same manner as in
Synthesis Example 2-14 except that the amount of Nippolan N-4009
added was changed to 212.9 parts by mass, the amount of
trimethylolpropane added was changed to 0.3 part by mass, the
amount of hexamethylene diisocyanate added was changed to 70.5
parts by mass, and the chain extending reaction with
diethylenetriamine was changed to chain extending reaction with
water.
[0161] The polyurethane water dispersions thus obtained were
measured in the same manners as in Synthesis Example 1-1 and the
like. The results are shown in Table 6.
TABLE-US-00006 TABLE 6 Acid value or Non- amine Amount of Amount
Polyurethane volatile value urethane of urea water content
Crosslinking (mgKOH/ bond bond dispersion (wt %) density g) (g/eq)
(g/eq) 2A 30 0.23 16 481 1,684 2B 30 0.23 23 232 1,282 2C 30 0.23
23 232 1,282 2D 30 0.23 23 232 1,282 2E 30 0.29 23 241 1,083 2F 30
0.14 23 269 2,807 2G 30 0.23 23 381 1,438 2H 30 0.24 23 459 2,425
2I 30 0.23 23 417 0 2J 30 0.23 23 282 1,295 2K 30 0.23 23 260 2,475
2L 30 0.23 23 260 1,303 2M 30 0 23 403 5,296 2N 30 0.92 23 362
1,162 2O 30 0.007 23 436 3,955
Production of Electrodes
[0162] Negative electrodes and positive electrodes were produced in
the following manner by using the polyurethane water dispersions
shown in Table 7 below as a binder.
TABLE-US-00007 TABLE 7 Kind of electrode Kind of binder negative
electrode 2-1 polyurethane water dispersion 2A negative electrode
2-2 polyurethane water dispersion 2B negative electrode 2-3
polyurethane water dispersion 2C negative electrode 2-4
polyurethane water dispersion 2D negative electrode 2-5
polyurethane water dispersion 2E negative electrode 2-6
polyurethane water dispersion 2F negative electrode 2-7
polyurethane water dispersion 2G negative electrode 2-8
polyurethane water dispersion 2H negative electrode 2-9
polyurethane water dispersion 2I negative electrode 2-10
polyurethane water dispersion 2J negative electrode 2-11
polyurethane water dispersion 2K negative electrode 2-12
polyurethane water dispersion 2L negative electrode 2-13
polyurethane water dispersion 2M negative electrode 2-14
polyurethane water dispersion 2N negative electrode 2-15
polyurethane water dispersion 2O negative electrode 2-16 SBR
negative electrode 2-17 polyurethane water dispersion 2G negative
electrode 2-18 SBR negative electrode 2-19 polyurethane water
dispersion 2G negative electrode 2-20 SBR positive electrode 2-1
PVDF positive electrode 2-2 polyurethane water dispersion 2G
positive electrode 2-3 polyurethane water dispersion 2O positive
electrode 2-4 PVDF positive electrode 2-5 polyurethane water
dispersion 2G positive electrode 2-6 PVDF positive electrode 2-7
polyurethane water dispersion 2G
Negative Electrode 2-1
[0163] With a planetary mixer, 100 g of natural graphite as a
negative electrode active substance, 0.5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 2% by mass aqueous solution of carboxymethyl
cellulose (CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku
Co., Ltd.) as a thickener, and 6.7 g of a 30% by mass solution of
the polyurethane water dispersion 2A as a binder were mixed to
prepare a negative electrode slurry having a solid content of 50%.
The negative electrode slurry was coated on an electrolytic copper
foil having a thickness of 10 .mu.m with a coating machine, dried
at 120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode 2-1 having a negative
electrode active substance in an amount of 7 mg/cm.sup.2.
Negative Electrodes 2-2 to 2-10 and 2-13 to 2-16
[0164] Negative electrodes were produced in the same manner as in
the negative electrode 2-1 except that the polyurethane water
dispersion 2A was changed to the polyurethane water dispersions or
the SBR latex shown in Table 7.
Negative Electrodes 2-11 and 2-12
[0165] With a planetary mixer, 100 g of natural graphite as a
negative electrode active substance, 0.5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 1% by mass aqueous solution of hydroxyethyl
cellulose (HEC) (HEC Daicel SP900, produced by Daicel Chemical
Industries, Ltd.) as a thickener, and 6.7 g of a 30% by mass
solution of the polyurethane water dispersion shown in Table 7 as a
binder were mixed to prepare a negative electrode slurry having a
solid content of 50%. The negative electrode slurry was coated on
an electrolytic copper foil having a thickness of 10 .mu.m with a
coating machine, dried at 120.degree. C., and then subjected to a
roll pressing treatment, thereby providing a negative electrode
having a negative electrode active substance in an amount of 7
mg/cm.sup.2.
Negative Electrode 2-17
[0166] With a planetary mixer, 100 g of SiO (average particle
diameter: 4.5 .mu.m, specific surface area: 5.5 m.sup.2/g) as a
negative electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent,
100 g of a 2% by mass aqueous solution of carboxymethyl cellulose
(CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.)
as a thickener, and 6.7 g of a 30% by mass solution of the
polyurethane water dispersion 2G as a binder were mixed to prepare
a negative electrode slurry having a solid content of 50%. The
negative electrode slurry was coated on an electrolytic copper foil
having a thickness of 10 .mu.m with a coating machine, dried at
120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode having a negative electrode
active substance in an amount of 2.5 mg/cm.sup.2.
Negative Electrode 2-18
[0167] A negative electrode was produced in the same manner as in
the negative electrode 2-17 except that the polyurethane water
dispersion 2G was changed to an SBR latex.
Negative Electrode 2-19
[0168] With a planetary mixer, 100 g of Li.sub.4Ti.sub.5O.sub.12 as
a negative electrode active substance, 5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 2% by mass aqueous solution of carboxymethyl
cellulose (CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku
Co., Ltd.) as a thickener, and 6.7 g of a 30% by mass solution of
the polyurethane water dispersion 2G as a binder were mixed to
prepare a negative electrode slurry having a solid content of 50%.
The negative electrode slurry was coated on an electrolytic copper
foil having a thickness of 10 .mu.m with a coating machine, dried
at 120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode having a negative electrode
active substance in an amount of 9.7 mg/cm.sup.2.
Negative Electrode 2-20
[0169] A negative electrode was produced in the same manner as in
the negative electrode 2-19 except that the polyurethane water
dispersion 2G was changed to an SBR latex.
Positive Electrode 2-1
[0170] With a planetary mixer, 100 g of
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 as a positive electrode
active substance, 7.8 g of carbon black (Super-P, produced by
Timcal Graphite & Carbon) as a conductive agent, 6 g of
polyvinylidene fluoride as a binder, and 61.3 g of
N-methyl-2-pyrrolidone as a dispersion medium were mixed to prepare
a positive electrode slurry having a solid content of 65%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 13.8 mg/cm.sup.2.
Positive Electrodes 2-2 and 2-3
[0171] With a planetary mixer, 100 g of
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 as a positive electrode
active substance, 7.8 g of carbon black (Super-P, produced by
Timcal Graphite & Carbon) as a conductive agent, 100 g of a 2%
by mass aqueous solution of carboxymethyl cellulose (Cellogen WS-C,
produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a thickener, and
6.7 g of a 30% by mass solution of the polyurethane water
dispersion shown in Table 7 as a binder were mixed to prepare a
positive electrode slurry having a solid content of 50%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 with a coating machine, dried at 130.degree. C.,
and then subjected to a roll pressing treatment, thereby providing
a positive electrode having a positive electrode active substance
in an amount of 13.8 mg/cm.sup.2.
Positive Electrode 2-4
[0172] With a planetary mixer, 100 g of LiMn.sub.2O.sub.4 as a
positive electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent, 6
g of polyvinylidene fluoride as a binder, and 59.8 g of
N-methyl-2-pyrrolidone as a dispersion medium were mixed to prepare
a positive electrode slurry having a solid content of 65%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 22 mg/cm.sup.2.
Positive Electrode 2-5
[0173] With a planetary mixer, 100 g of LiMn.sub.2O.sub.4 as a
positive electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent,
100 g of a 2% by mass aqueous solution of carboxymethyl cellulose
(Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a
thickener, and 6.7 g of a 30% by mass solution of the polyurethane
water dispersion 2G as a binder were mixed to prepare a positive
electrode slurry having a solid content of 50%. The positive
electrode slurry was coated on an aluminum foil having a thickness
of 20 .mu.m with a coating machine, dried at 130.degree. C., and
then subjected to a roll pressing treatment, thereby providing a
positive electrode having a positive electrode active substance in
an amount of 22 mg/cm.sup.2.
Positive Electrode 2-6
[0174] With a planetary mixer, 100 g of LiFeOP.sub.4 as a positive
electrode active substance, 5 g of carbon black (Super-P, produced
by Timcal Graphite & Carbon) as a conductive agent, 6 g of
polyvinylidene fluoride as a binder, and 135.7 g of
N-methyl-2-pyrrolidone as a dispersion medium were mixed to prepare
a positive electrode slurry having a solid content of 45%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 14.5 mg/cm.sup.2.
Positive Electrode 2-7
[0175] With a planetary mixer, 100 g of LiFeOP.sub.4 as a positive
electrode active substance, 5 g of carbon black (Super-P, produced
by Timcal Graphite & Carbon) as a conductive agent, 100 g of a
2% by mass aqueous solution of carboxymethyl cellulose (Cellogen
WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a thickener,
and 6.7 g of a 30% by mass solution of the polyurethane water
dispersion 2G as a binder were mixed to prepare a positive
electrode slurry having a solid content of 50%. The positive
electrode slurry was coated on an aluminum foil having a thickness
of 20 .mu.m with a coating machine, dried at 130.degree. C., and
then subjected to a roll pressing treatment, thereby providing a
positive electrode having a positive electrode active substance in
an amount of 14.5 mg/cm.sup.2.
Evaluation of Electrode
[0176] The electrodes thus obtained were subjected to the
evaluation of the binding capability and the evaluation of the
resistance to an electrolytic solution in the same manner as in
Example 1-1 and the like. The evaluation results are shown in Table
8.
TABLE-US-00008 TABLE 8 Evaluation Evaluation of of resistance to
binding electrolytic Kind of electrode capability solution Example
2-1 negative electrode 2-1 4 A Example 2-2 negative electrode 2-2 4
A Example 2-3 negative electrode 2-3 4 A Example 2-4 negative
electrode 2-4 5 A Example 2-5 negative electrode 2-5 4 A Example
2-6 negative electrode 2-6 5 A Example 2-7 negative electrode 2-7 5
A Example 2-8 negative electrode 2-8 4 A Example 2-9 negative
electrode 2-9 4 A Example 2-10 negative electrode 2-10 4 A Example
2-11 negative electrode 2-11 4 A Example 2-12 negative electrode
2-12 4 A Example 2-13 negative electrode 2-17 4 A Example 2-14
negative electrode 2-19 4 A Example 2-15 positive electrode 2-2 5 A
Example 2-16 positive electrode 2-5 5 A Example 2-17 positive
electrode 2-7 4 A Comparative negative electrode 2-16 3 A Example
2-1 Comparative negative electrode 2-18 3 A Example 2-2 Comparative
negative electrode 2-20 3 A Example 2-3 Comparative positive
electrode 2-1 3 A Example 2-4 Comparative positive electrode 2-4 3
A Example 2-5 Comparative positive electrode 2-6 3 A Example
2-6
Production and Evaluation of Lithium Secondary Battery
[0177] Lithium batteries were produced in the same manner as in
Example 1-1 and the like except that the negative electrodes and
the positive electrodes shown in Table 9 were used, and evaluated
for battery capability. In the evaluation for battery capability,
the cell impedance was measured, and the capacity retention after
the charge and discharge cycles was measured, in the same manner as
in Examples above. The results are shown in Table 10.
TABLE-US-00009 TABLE 9 Constitution of electrodes Negative
electrode Positive electrode Example 2-18 negative electrode 2-1
positive electrode 2-1 Example 2-19 negative electrode 2-2 positive
electrode 2-1 Example 2-20 negative electrode 2-3 positive
electrode 2-1 Example 2-21 negative electrode 2-4 positive
electrode 2-1 Example 2-22 negative electrode 2-5 positive
electrode 2-1 Example 2-23 negative electrode 2-6 positive
electrode 2-1 Example 2-24 negative electrode 2-7 positive
electrode 2-1 Example 2-25 negative electrode 2-8 positive
electrode 2-1 Example 2-26 negative electrode 2-9 positive
electrode 2-1 Example 2-27 negative electrode 2-10 positive
electrode 2-1 Example 2-28 negative electrode 2-11 positive
electrode 2-1 Example 2-29 negative electrode 2-12 positive
electrode 2-1 Example 2-30 negative electrode 2-17 positive
electrode 2-1 Example 2-31 negative electrode 2-19 positive
electrode 2-1 Example 2-32 negative electrode 2-16 positive
electrode 2-2 Example 2-33 negative electrode 2-16 positive
electrode 2-5 Example 2-34 negative electrode 2-16 positive
electrode 2-7 Example 2-35 negative electrode 2-7 positive
electrode 2-2 Comparative Example negative electrode 2-16 positive
electrode 2-1 2-7 Comparative Example negative electrode 2-18
positive electrode 2-1 2-8 Comparative Example negative electrode
2-20 positive electrode 2-1 2-9 Comparative Example negative
electrode 2-16 positive electrode 2-4 2-10 Comparative Example
negative electrode 2-16 positive electrode 2-6 2-11
TABLE-US-00010 TABLE 10 Evaluation of battery Capacity retention
Cell impedance after charge (m.OMEGA./1 kHz) and discharge cycles
(%) Example 2-18 210 93.9 Example 2-19 204 94.1 Example 2-20 202
94.3 Example 2-21 210 93.9 Example 2-22 202 94.4 Example 2-23 198
94.9 Example 2-24 188 96.3 Example 2-25 198 95.0 Example 2-26 200
94.4 Example 2-27 193 95.6 Example 2-28 201 94.3 Example 2-29 198
95.2 Example 2-30 209 93.8 Example 2-31 190 96.2 Example 2-32 194
95.5 Example 2-33 196 95.2 Example 2-34 186 96.2 Example 2-35 195
95.3 Comparative Example 2-7 230 91.1 Comparative Example 2-8 248
87.2 Comparative Example 2-9 220 92.5 Comparative Example 2-10 236
89.3 Comparative Example 2-11 234 89.6
Synthesis of Aqueous Resin Composition
Synthesis Example 3-1
[0178] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 145 parts by
mass of Newpol BPE-20NK (an ethylene oxide adduct of bisphenol A,
produced by Sanyo Chemical Industries, Ltd., average hydroxyl group
value: 360 mgKOH/g, number of active hydrogen group: 2), 9.5 parts
by mass of trimethylolpropane (number of active hydrogen group: 3),
16.3 parts by mass of dimethylolpropionic acid (number of active
hydrogen group: 2), 129.2 parts by mass of hexamethylene
diisocyanate, and 200 parts by mass of methyl ethyl ketone were
placed, and reacted at 75.degree. C. for 4 hours to provide a
methyl ethyl ketone solution of a urethane prepolymer having a free
isocyanate group content of 3.5% with respect to the nonvolatile
component. The solution was cooled to 45.degree. C. and neutralized
by adding 12.3 parts by mass of triethylamine, and then 300 parts
by mass of methyl methacrylate was added thereto. Subsequently, the
solution was emulsified and dispersed with a homogenizer while
adding 1,200 parts by mass of water thereto, and an amine aqueous
solution containing 6.8 parts by mass of ethylenediamine (number of
active hydrogen group: 2) diluted with 100 parts by mass of water
was added thereto for performing chain extending reaction for 1
hour. Subsequently, 1.0 part by mass of t-butyl hydroperoxide and
1.0 part by mass of sodium sulfite were added, and the unsaturated
polymerizable monomer was polymerized by performing reaction at
25.degree. C. for 3 hours. The solvent was removed by heating to
50.degree. C. under reduced pressure, thereby providing an aqueous
resin composition 3A having a nonvolatile content of approximately
30%. The resulting aqueous resin composition has a mass ratio
(X)/(Y) of the polymer of the unsaturated polymerizable monomer (X)
and the hydrophilic group-containing polyurethane (Y) of 40/60.
Synthesis Example 3-2
[0179] An aqueous resin composition 3B having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-1
except that 145 parts by mass of Newpol BPE-20NK (an ethylene oxide
adduct of bisphenol A, produced by Sanyo Chemical Industries, Ltd.,
average hydroxyl group value: 360 mgKOH/g, number of active
hydrogen group: 2) was changed to 140.7 parts by mass thereof, 9.5
parts by mass of trimethylolpropane (number of active hydrogen
group: 3) was changed to 13.8 parts by mass of
1,4-cyclohexanedimethanol (number of active hydrogen group: 2), and
6.8 parts by mass of ethylenediamine (number of active hydrogen
group: 2) was changed to 9.1 parts by mass of
diethylenetriamine.
Synthesis Example 3-3
[0180] An aqueous resin composition 3C having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-1
except that 145 parts by mass of Newpol BPE-20NK (an ethylene oxide
adduct of bisphenol A, produced by Sanyo Chemical Industries, Ltd.,
average hydroxyl group value: 360 mgKOH/g, number of active
hydrogen group: 2) was changed to 36.9 parts by mass of
Adekapolyether BPX-11 (a trade name, a propylene oxide adduct of
bisphenol A, produced by Adeka Corporation, average hydroxyl group
value: 312 mgKOH/g, number of active hydrogen group: 2) and 105.5
parts by mass of Teslac 2477 (a trade name, a polyester polyol
formed of 1,6-hexanediol, adipic acid and isophthalic acid,
produced by Hitachi Kasei Polymer Co., Ltd., average hydroxyl group
value: 64 mgKOH/g, number of active hydrogen group: 2), 129.2 parts
by mass of hexamethylene diisocyanate was changed to 131.8 parts by
mass of dicyclohexylmethane diisocyanate, and 6.8 parts by mass of
ethylenediamine (number of active hydrogen group: 2) was changed to
6.0 parts by mass thereof.
Synthesis Example 3-4
[0181] An aqueous resin composition 3D having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-1
except that 145 parts by mass of Newpol BPE-20NK (an ethylene oxide
adduct of bisphenol A, produced by Sanyo Chemical Industries, Ltd.,
average hydroxyl group value: 360 mgKOH/g, number of active
hydrogen group: 2) was changed to 114.0 parts by mass of
Adekapolyether BPX-11 (a trade name, a propylene oxide adduct of
bisphenol A, produced by Adeka Corporation, average hydroxyl group
value: 312 mgKOH/g, number of active hydrogen group: 2) and 60.0
parts by mass of Nippolan N-4009 (a trade name, a polyester polyol
formed of 1,4-butanediol and adipic acid, produced by Nippon
Polyurethane Industry Co., Ltd., average hydroxyl group value: 112
mgKOH/g, number of active hydrogen group: 2), 9.5 parts by mass of
trimethylolpropane (number of active hydrogen group: 3) was changed
to 5.5 parts by mass of 1,4-cyclohexanedimethanol (number of active
hydrogen group: 2), 129.2 parts by mass of hexamethylene
diisocyanate was changed to 104.2 parts by mass thereof, the chain
extension was changed to water extension, and 300 parts by mass of
methyl methacrylate was changed to 150 parts by mass of methyl
methacrylate and 50 parts by mass of styrene.
Synthesis Example 3-5
[0182] An aqueous resin composition 3E having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-1
except that 145 parts by mass of Newpol BPE-20NK (an ethylene oxide
adduct of bisphenol A, produced by Sanyo Chemical Industries, Ltd.,
average hydroxyl group value: 360 mgKOH/g, number of active
hydrogen group: 2) was changed to 145.2 parts by mass of Nippolan
N-4009 (a trade name, a polyester polyol formed of 1,4-butanediol
and adipic acid, produced by Nippon Polyurethane Industry Co.,
Ltd., average hydroxyl group value: 112 mgKOH/g, number of active
hydrogen group: 2), 129.2 parts by mass of hexamethylene
diisocyanate was changed to 129.0 parts by mass of
dicyclohexylmethane diisocyanate, 6.8 parts by mass of
ethylenediamine (number of active hydrogen group: 2) was changed to
6.4 parts by mass thereof, and 300 parts by mass of methyl
methacrylate was changed to 150 parts by mass of methyl
methacrylate and 50 parts by mass of styrene.
Synthesis Example 3-6
[0183] An aqueous resin composition 3F having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-5
except that 145.2 parts by mass of Nippolan N-4009 (a trade name, a
polyester polyol formed of 1,4-butanediol and adipic acid, produced
by Nippon Polyurethane Industry Co., Ltd., average hydroxyl group
value: 112 mgKOH/g, number of active hydrogen group: 2) was changed
to 145.2 parts by mass of Eternacoll UH-100 (a trade name, a
polycarbonate polyol formed of 1,6-hexanediol as constitutional
component, produced by Ube Industries, Ltd., average hydroxyl group
value: 110 mgKOH/g, number of active hydrogen group: 2), and 50
parts by mass of styrene was changed to 50 parts by mass of butyl
methacrylate.
Synthesis Example 3-7
[0184] An aqueous resin composition 3G having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-6
except that 50 parts by mass of butyl methacrylate was changed to
50 parts by mass of phenoxymethyl methacrylate (NK Ester PHE-1G, a
trade name, produced by Shin-Nakamura Chemical Co., Ltd.).
Synthesis Example 3-8
[0185] An aqueous resin composition 3H having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-6
except that 50 parts by mass of butyl methacrylate was changed to
50 parts by mass of styrene.
Synthesis Example 3-9
[0186] An aqueous resin composition 3I having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-6
except that 150 parts by mass of methyl methacrylate and 50 parts
by mass of butyl methacrylate were changed to 200 parts by mass of
methyl methacrylate, 50 parts by mass of styrene, 48 parts by mass
of butadiene and 2 parts by mass of 2-methacryloxyethyl phthalate
(NK Ester CB-1, a trade name, produced by Shin-Nakamura Chemical
Co., Ltd.), and 1,200 parts by mass of water was changed to 1,500
parts by mass thereof. The resulting aqueous resin composition has
a mass ratio (X)/(Y) of the polymer of the unsaturated
polymerizable monomer (X) and the hydrophilic group-containing
polyurethane (Y) of 50/50.
Synthesis Example 3-10
[0187] An aqueous resin composition 3J having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-6
except that 150 parts by mass of methyl methacrylate and 50 parts
by mass of butyl methacrylate were changed to 150 parts by mass of
methyl methacrylate, 150 parts by mass of styrene, 147 parts by
mass of butadiene and 3.0 parts by mass of Aqualon KH-05 (a trade
name, polyoxyethylene-1-(allyloxymethyl)alkyl ether ammonium
sulfate, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.), and 1,200
parts by mass of water was changed to 1,800 parts by mass thereof.
The resulting aqueous resin composition has a mass ratio (X)/(Y) of
the polymer of the unsaturated polymerizable monomer (X) and the
hydrophilic group-containing polyurethane (Y) of 60/40.
Synthesis Example 3-11
[0188] An aqueous resin composition 3K having a nonvolatile content
of 30% was produced in the same manner as in Synthesis Example 3-6
except that 150 parts by mass of methyl methacrylate and 50 parts
by mass of butyl methacrylate were changed to 300 parts by mass of
styrene, 147 parts by mass of butadiene and Aqualon BC-05 (a trade
name, polyoxyethylene nonyl propenyl phenyl ether ammonium sulfate,
produced by Dai-ichi Kogyo Seiyaku Co., Ltd.), and 1,200 parts by
mass of water was changed to 1,800 parts by mass thereof. The
resulting aqueous resin composition has a mass ratio (X)/(Y) of the
polymer of the unsaturated polymerizable monomer (X) and the
hydrophilic group-containing polyurethane (Y) of 60/40.
Synthesis Example 3-12
[0189] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 206.2 parts
by mass of Nippolan N-4009 (number of active hydrogen group: 2),
5.5 parts by mass of 1,4-cyclohexanedimethanol (number of active
hydrogen group: 2), 16.3 parts by mass of dimethylolpropionic acid
(number of active hydrogen group: 2), 72 parts by mass of
hexamethylene diisocyanate, and 200 parts by mass of methyl ethyl
ketone were placed, and reacted at 75.degree. C. for 4 hours to
provide a methyl ethyl ketone solution of a urethane prepolymer
having a free isocyanate group content of 2.3% with respect to the
nonvolatile component. The solution was cooled to 45.degree. C. and
neutralized by adding 12.3 parts by mass of triethylamine, and was
then emulsified and dispersed with a homogenizer while gradually
adding 900 parts by mass of water thereto, thereby performing chain
extending reaction with water (number of active hydrogen group: 2)
for 1 hour. The solvent was removed by heating to 50.degree. C.
under reduced pressure, thereby providing a polyurethane water
dispersion 3L having a nonvolatile content of approximately
30%.
Synthesis Example 3-13
[0190] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 181.7 parts
by mass of Nippolan N-4009 (number of active hydrogen group: 2),
9.5 parts by mass of trimethylolpropane (number of active hydrogen
group: 3), 16.3 parts by mass of dimethylolpropionic acid (number
of active hydrogen group: 2), 92.5 parts by mass of hexamethylene
diisocyanate, and 200 parts by mass of methyl ethyl ketone were
placed, and reacted at 75.degree. C. for 4 hours to provide a
methyl ethyl ketone solution of a urethane prepolymer having a free
isocyanate group content of 3.8% with respect to the nonvolatile
component. The solution was cooled to 45.degree. C. and neutralized
by adding 12.3 parts by mass of triethylamine, and was then
emulsified and dispersed with a homogenizer while gradually adding
900 parts by mass of water thereto, and an amine aqueous solution
containing 7.8 parts by mass of diethylenetriamine (number of
active hydrogen group: 3) diluted with 100 parts by mass of water
was added thereto, thereby performing chain extending reaction for
1 hour. The solvent was removed by heating to 50.degree. C. under
reduced pressure, thereby providing a polyurethane water dispersion
3M having a nonvolatile content of approximately 30%.
Synthesis Example 3-14
[0191] In a four-neck flask equipped with a stirrer, a reflux
condenser, a thermometer and a nitrogen blowing tube, 212.9 parts
by mass of Nippolan N-4009 (number of active hydrogen group: 2),
0.3 part by mass of trimethylolpropane (number of active hydrogen
group: 3), 16.3 parts by mass of dimethylolpropionic acid (number
of active hydrogen group: 2), 70.5 parts by mass of hexamethylene
diisocyanate, and 200 parts by mass of methyl ethyl ketone were
placed, and reacted at 75.degree. C. for 4 hours to provide a
methyl ethyl ketone solution of a urethane prepolymer having a free
isocyanate group content of 2.1% with respect to the nonvolatile
component. The solution was cooled to 45.degree. C. and neutralized
by adding 12.3 parts by mass of triethylamine, and was then
emulsified and dispersed with a homogenizer while gradually adding
900 parts by mass of water thereto, thereby performing chain
extending reaction with water (number of active hydrogen group: 2)
for 1 hour. The solvent was removed by heating to 50.degree. C.
under reduced pressure, thereby providing a polyurethane water
dispersion 3N having a nonvolatile content of approximately
30%.
Evaluation of Aqueous Resin Composition
[0192] The mass of the nonvolatile content of the aqueous resin
composition thus obtained was measured according to JIS K6828. The
aqueous resin compositions were subjected to the following
measurements. The results are shown in Table 11.
[0193] The crosslinking density of the polyurethane contained in
the aqueous resin composition was calculated by the expression 1
shown above.
[0194] The acid value, the amount of urethane bond, and the amount
of urea bond of the polyurethane contained in the aqueous resin
composition were calculated from the charged amounts in the
synthesis of the urethane resin and the free isocyanate group
content with respect to the nonvolatile content after the
reaction.
TABLE-US-00011 TABLE 11 Aqueous Acid value Amount of Amount of urea
resin Crosslinking (mgKOH/ urethane bond bond composition density
g) (g/eq) (g/eq) 3A 0.23 23 232 1,282 3B 0.29 23 241 1,083 3C 0.23
23 381 1,298 3D 0 23 266 5,333 3E 0.23 23 398 1,372 3F 0.23 23 398
1,372 3G 0.23 23 398 1,372 3H 0.23 23 398 1,372 3I 0.23 23 398
1,372 3J 0.23 23 398 1,372 3K 0.23 23 398 1,372 3L 0 23 403 5,296
3M 0.92 23 362 1,162 3N 0.007 23 436 3,955
Production of Electrodes
[0195] Negative electrodes and positive electrodes were produced in
the following manner by using the aqueous resin compositions shown
in Table 12 below as a binder.
TABLE-US-00012 TABLE 12 Kind of electrode Kind of binder negative
electrode 3-1 aqueous resin composition 3A negative electrode 3-2
aqueous resin composition 3B negative electrode 3-3 aqueous resin
composition 3C negative electrode 3-4 aqueous resin composition 3D
negative electrode 3-5 aqueous resin composition 3E negative
electrode 3-6 aqueous resin composition 3F negative electrode 3-7
aqueous resin composition 3G negative electrode 3-8 aqueous resin
composition 3H negative electrode 3-9 aqueous resin composition 3I
negative electrode 3-10 aqueous resin composition 3J negative
electrode 3-11 aqueous resin composition 3K negative electrode 3-12
aqueous resin composition 3L negative electrode 3-13 aqueous resin
composition 3M negative electrode 3-14 aqueous resin composition 3N
negative electrode 3-15 SBR negative electrode 3-16 aqueous resin
composition 3F negative electrode 3-17 SBR negative electrode 3-18
aqueous resin composition 3F negative electrode 3-19 SBR positive
electrode 3-1 PVDF positive electrode 3-2 aqueous resin composition
3F positive electrode 3-3 aqueous resin composition 3M positive
electrode 3-4 PVDF positive electrode 3-5 aqueous resin composition
3I positive electrode 3-6 PVDF positive electrode 3-7 aqueous resin
composition 3G
Negative Electrode 3-1
[0196] With a planetary mixer, 100 g of natural graphite as a
negative electrode active substance, 0.5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 2% by mass aqueous solution of carboxymethyl
cellulose (CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku
Co., Ltd.) as a thickener, and 6.7 g of a 30% by mass solution of
the aqueous resin composition 3A as a binder were mixed to prepare
a negative electrode slurry having a solid content of 50%. The
negative electrode slurry was coated on an electrolytic copper foil
having a thickness of 10 .mu.m with a coating machine, dried at
120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode 3-1 having a negative
electrode active substance in an amount of 7 mg/cm.sup.2.
Negative Electrodes 3-2 to 3-15
[0197] Negative electrodes were produced in the same manner as in
the negative electrode 3-1 except that the aqueous resin
composition 3A was changed to the aqueous resin compositions or the
SBR latex shown in Table 12.
Negative Electrode 3-16
[0198] With a planetary mixer, 100 g of SiO (average particle
diameter: 4.5 .mu.m, specific surface area: 5.5 m.sup.2/g) as a
negative electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent,
100 g of a 2% by mass aqueous solution of carboxymethyl cellulose
(CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.)
as a thickener, and 6.7 g of a 30% by mass solution of the aqueous
resin composition 3F as a binder were mixed to prepare a negative
electrode slurry having a solid content of 50%. The negative
electrode slurry was coated on an electrolytic copper foil having a
thickness of 10 .mu.m with a coating machine, dried at 120.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a negative electrode having a negative electrode active
substance in an amount of 2.5 mg/cm.sup.2.
Negative Electrode 3-17
[0199] A negative electrode was produced in the same manner as in
the negative electrode 3-16 except that the aqueous resin
composition was changed to an SBR latex.
Negative Electrode 3-18
[0200] With a planetary mixer, 100 g of Li.sub.4Ti.sub.5O.sub.12 as
a negative electrode active substance, 5 g of carbon black
(Super-P, produced by Timcal Graphite & Carbon) as a conductive
agent, 100 g of a 2% by mass aqueous solution of carboxymethyl
cellulose (CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku
Co., Ltd.) as a thickener, and 6.7 g of a 30% by mass solution of
the aqueous resin composition 3F as a binder were mixed to prepare
a negative electrode slurry having a solid content of 50%. The
negative electrode slurry was coated on an electrolytic copper foil
having a thickness of 10 .mu.m with a coating machine, dried at
120.degree. C., and then subjected to a roll pressing treatment,
thereby providing a negative electrode having a negative electrode
active substance in an amount of 9.7 mg/cm.sup.2.
Negative Electrode 3-19
[0201] A negative electrode was produced in the same manner as in
the negative electrode 3-18 except that the aqueous resin
composition was changed to an SBR latex.
Positive Electrode 3-1
[0202] With a planetary mixer, 100 g of
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 as a positive electrode
active substance, 7.8 g of carbon black (Super-P, produced by
Timcal Graphite & Carbon) as a conductive agent, 6 g of
polyvinylidene fluoride as a binder, and 61.3 g of
N-methyl-2-pyrrolidone (NMP) as a dispersion medium were mixed to
prepare a positive electrode slurry having a solid content of 65%.
The positive electrode slurry was coated on an aluminum foil having
a thickness of 20 .mu.m with a coating machine, dried at
130.degree. C., and then subjected to a roll pressing treatment,
thereby providing a positive electrode having a positive electrode
active substance in an amount of 13.8 mg/cm.sup.2.
Positive Electrodes 3-2 and 3-3
[0203] With a planetary mixer, 100 g of
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 as a positive electrode
active substance, 7.8 g of carbon black (Super-P, produced by
Timcal Graphite & Carbon) as a conductive agent, 100 g of a 2%
by mass aqueous solution of carboxymethyl cellulose (CMC) (Cellogen
WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a thickener,
and 6.7 g of a 30% by mass solution of the aqueous resin
composition shown in Table 12 as a binder were mixed to prepare a
positive electrode slurry having a solid content of 50%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 13.8 mg/cm.sup.2.
Positive Electrode 3-4
[0204] With a planetary mixer, 100 g of LiMn.sub.2O.sub.4 as a
positive electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent, 6
g of polyvinylidene fluoride as a binder, and 59.8 g of
N-methyl-2-pyrrolidone (NMP) as a dispersion medium were mixed to
prepare a positive electrode slurry having a solid content of 65%.
The positive electrode slurry was coated on an aluminum foil having
a thickness of 20 .mu.m with a coating machine, dried at
130.degree. C., and then subjected to a roll pressing treatment,
thereby providing a positive electrode having a positive electrode
active substance in an amount of 22 mg/cm.sup.2.
Positive Electrode 3-5
[0205] With a planetary mixer, 100 g of LiMn.sub.2O.sub.4 as a
positive electrode active substance, 5 g of carbon black (Super-P,
produced by Timcal Graphite & Carbon) as a conductive agent,
100 g of a 2% by mass aqueous solution of carboxymethyl cellulose
(CMC) (Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.)
as a thickener, and 6.7 g of a 30% by mass solution of the aqueous
resin composition 3I shown in Table 12 as a binder were mixed to
prepare a positive electrode slurry having a solid content of 50%.
The positive electrode slurry was coated on an aluminum foil having
a thickness of 20 .mu.m with a coating machine, dried at
130.degree. C., and then subjected to a roll pressing treatment,
thereby providing a positive electrode having a positive electrode
active substance in an amount of 22 mg/cm.sup.2.
Positive Electrode 3-6
[0206] With a planetary mixer, 100 g of LiFeOP.sub.4 as a positive
electrode active substance, 5 g of carbon black (Super-P, produced
by Timcal Graphite & Carbon) as a conductive agent, 6 g of
polyvinylidene fluoride as a binder, and 135.7 g of
N-methyl-2-pyrrolidone (NMP) as a dispersion medium were mixed to
prepare a positive electrode slurry having a solid content of 45%.
The positive electrode slurry was coated on an aluminum foil having
a thickness of 20 .mu.m with a coating machine, dried at
130.degree. C., and then subjected to a roll pressing treatment,
thereby providing a positive electrode having a positive electrode
active substance in an amount of 14.5 mg/cm.sup.2.
Positive Electrode 3-7
[0207] With a planetary mixer, 100 g of LiFeOP.sub.4 as a positive
electrode active substance, 5 g of carbon black (Super-P, produced
by Timcal Graphite & Carbon) as a conductive agent, 100 g of a
2% by mass aqueous solution of carboxymethyl cellulose (CMC)
(Cellogen WS-C, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a
thickener, and 6.7 g of a 30% by mass solution of the aqueous resin
composition 3G shown in Table 12 as a binder were mixed to prepare
a positive electrode slurry having a solid content of 50%. The
positive electrode slurry was coated on an aluminum foil having a
thickness of 20 .mu.m with a coating machine, dried at 130.degree.
C., and then subjected to a roll pressing treatment, thereby
providing a positive electrode having a positive electrode active
substance in an amount of 14.5 mg/cm.sup.2.
Evaluation of Electrode
[0208] The electrodes thus obtained were subjected to the
evaluation of the binding capability and the evaluation of the
resistance to an electrolytic solution in the same manner as above.
The evaluation results are shown in Table 13.
TABLE-US-00013 TABLE 13 Evaluation Evaluation of of resistance to
binding electrolytic Kind of electrode capability solution Example
3-1 negative electrode 3-1 4 A Example 3-2 negative electrode 3-2 4
A Example 3-3 negative electrode 3-3 4 A Example 3-4 negative
electrode 3-4 4 A Example 3-5 negative electrode 3-5 4 A Example
3-6 negative electrode 3-6 4 A Example 3-7 negative electrode 3-7 5
A Example 3-8 negative electrode 3-8 4 A Example 3-9 negative
electrode 3-9 5 A Example 3-10 negative electrode 3-10 4 A Example
3-11 negative electrode 3-11 4 A Example 3-12 negative electrode
3-16 4 A Example 3-13 negative electrode 3-18 4 A Example 3-14
positive electrode 3-2 5 A Example 3-15 positive electrode 3-5 4 A
Example 3-16 positive electrode 3-7 4 A Comparative negative
electrode 3-15 3 A Example 3-1 Comparative negative electrode 3-17
3 B Example 3-2 Comparative negative electrode 3-19 3 A Example 3-3
Comparative positive electrode 3-1 3 A Example 3-4 Comparative
positive electrode 3-4 3 A Example 3-5 Comparative positive
electrode 3-6 3 A Example 3-6
Production and Evaluation of Lithium Secondary Battery
[0209] Lithium batteries were produced in the same manner as in
Example 1-1 and the like except that the negative electrodes and
the positive electrodes shown in Table 14 were used, and evaluated
for battery capability. In the evaluation for battery capability,
the cell impedance was measured, and the capacity retention after
the charge and discharge cycles was measured, in the same manner as
in Examples above. The results are shown in Table 15.
TABLE-US-00014 TABLE 14 Constitution of electrodes Negative
electrode Positive electrode Example 3-17 negative electrode 3-1
positive electrode 3-1 Example 3-18 negative electrode 3-2 positive
electrode 3-1 Example 3-19 negative electrode 3-3 positive
electrode 3-1 Example 3-20 negative electrode 3-4 positive
electrode 3-1 Example 3-21 negative electrode 3-5 positive
electrode 3-1 Example 3-22 negative electrode 3-6 positive
electrode 3-1 Example 3-23 negative electrode 3-7 positive
electrode 3-1 Example 3-24 negative electrode 3-8 positive
electrode 3-1 Example 3-25 negative electrode 3-9 positive
electrode 3-1 Example 3-26 negative electrode 3-10 positive
electrode 3-1 Example 3-27 negative electrode 3-11 positive
electrode 3-1 Example 3-28 negative electrode 3-16 positive
electrode 3-1 Example 3-29 negative electrode 3-18 positive
electrode 3-1 Example 3-30 negative electrode 3-15 positive
electrode 3-2 Example 3-31 negative electrode 3-15 positive
electrode 3-5 Example 3-32 negative electrode 3-15 positive
electrode 3-7 Example 3-33 negative electrode 3-6 positive
electrode 3-2 Comparative Example negative electrode 3-15 positive
electrode 3-1 3-7 Comparative Example negative electrode 3-17
positive electrode 3-1 3-8 Comparative Example negative electrode
3-19 positive electrode 3-1 3-9 Comparative Example negative
electrode 3-15 positive electrode 3-4 3-10 Comparative Example
negative electrode 3-15 positive electrode 3-6 3-11
TABLE-US-00015 TABLE 15 Evaluation of battery Cell impedance
Capacity retention after charge (m.OMEGA./1 kHz) and discharge
cycles (%) Example 3-17 218 93.8 Example 3-18 215 94.2 Example 3-19
196 95.0 Example 3-20 221 93.1 Example 3-21 208 94.8 Example 3-22
188 96.5 Example 3-23 198 95.8 Example 3-24 189 96.7 Example 3-25
192 95.8 Example 3-26 186 96.8 Example 3-27 191 96.4 Example 3-28
212 93.1 Example 3-29 192 96.7 Example 3-30 195 95.2 Example 3-31
202 94.7 Example 3-32 193 96.1 Example 3-33 197 95.2 Comparative
Example 230 91.3 3-7 Comparative Example 248 87.2 3-8 Comparative
Example 220 92.5 3-9 Comparative Example 236 89.3 3-10 Comparative
Example 234 89.6 3-11
[0210] It is understood from the results shown in Table 15 that as
compared to the use of an SBR latex or polyvinylidene fluoride
having been used, the use of the aqueous resin composition of the
invention provides more excellent binding capability, a lower cell
impedance, and a higher capacity retention after the charge and
discharge cycles.
INDUSTRIAL APPLICABILITY
[0211] The binder of the invention may be utilized as a binder for
an electrode of a lithium secondary battery, and an electrode
produced therewith may be used for production of various lithium
secondary batteries. The resulting lithium secondary batteries may
be applied to various portable equipments, such as a portable
telephone, a notebook computer, a personal digital assistant (PDA),
a camcorder and a digital still camera, and may also be used as
middle-size or large-size lithium secondary batteries for use in an
electric power-assisted bicycle, an electrically powered automobile
and the like.
* * * * *